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Contents
1. 711 118 711 100 711 135 such that the presence and status of the transportable 58 Field of Search 713 1 2 711 135 memory apparatus can be detected in order to permit the 711 100 103 118 154 710 10 computer system that includes the transportable memory apparatus to be appropriately initialized As such methods 56 References Cited for initializing a computer system that may include a trans U S PATENT DOCUMENTS 5 056 001 A 10 1991 Sexton 710 10 NON VOLATILE MEMORY BATTERY POWER MODULE VOLTAGE COMPARATOR SYSTEM BUS portable memory apparatus are also provided 15 Claims 8 Drawing Sheets MEMORY STORAGE 207 MODULE SOURCE SELECTION MODULE 40 MODULE TRANSPORTABLE MEMORY MODULE jeu iyw reed SYSTEM POWER SUPPLY US 6 557 077 Sheet 1 of 8 Apr 29 2003 U S Patent Luv L Old 5 W31SAS NIVW WALSAS LINN AMOINSIN HS3H33H 11 2 92 1 041 081 Tas WU3TIOHINO US 6 557 077 Sheet 2 of 8 Apr 29 2003 U S Patent L 15 913 5 4I3MOd W31SAS Sn8 1051405 6 o 5 m2. 78 US 6 557 077 Sheet 6 of 8 Apr 29 2003 U S Patent WO NI S3SVNI SHVMINHIJ Ad 3A THLO AHONWGIN 6 NI SH31SIO3H H3TIOHLINOO 993 dnidS ASOWAN IVILINI 97014 YATIONLNOD HSdHJdH AYOWAW 3ZITVILINI 9 139 13S CAHOW3IN NI VLVO ALYIG SV149 AdS i s P in viva 3401 4 EE HLIM H3TIOHLNOO aeo race AMOWSW 3ZITVILINI 2 a1naow S3 IVA JO 3dAL H3TIOW LNOO 9 3715 103130 AYOWSW 32 7 a 86 16 56 AYOWSW 095 9933 1HOd 5 S391430 US 6 557 077 Sheet 7 of 8 Apr 29 2003 U S Patent rS 90 8v OL NWO 138 OL HSNI 13S OL NYO ias QlTVAN I OL NYO 138 15 ON ON ON HOuH3 OL HSM14 NYO 9v 135 ISSA Q3143SSV 11934 5 61435344 naa 1 S3A 1195 Naad 318vN3 SVH 55 S 17 2 913 OL NVO 13S 15 OL 135 80 05 S3A 2135 5 1 353 AYLINOUID nas SI 21435388 ON SI 5 Sv m 0 OL HSNI NYO 195 e U S Patent Apr 2
3. 9 An apparatus according to claim 8 further comprising third determination means for determination means for determining if the transportable memory module has been transported from a second computer system to the first computer system if a transportable memory module is present 10 An apparatus according to claim 9 wherein the first computer system also includes a non volatile memory device and wherein the third determination means com prises means for comparing configuration information stored by the transportable memory module and the non volatile memory device means for determining that the transportable memory module has been transported if the configuration infor mation stored by the transportable memory module and the non volatile memory device are different and means for determining that the transportable memory module has not been transported if the configuration information stored by the transportable memory mod ule and the non volatile memory device match 11 An apparatus according to claim 10 further comprising restoration means for restoring the configuration informa tion of the non volatile memory device by copying the configuration information of the transportable memory mod ule to the non volatile memory device if the transportable memory module has been transported from a second com puter system to the first computer system and if the con figuration information stored by the transportable memory module and
4. amp gt 318VlHOdSNVHL WOLVuvdWOO 31naow annaow ADVLIOA 3 IL V 10A lx NON anmnnaow ANHOW3MN uc NOILO3 13S 329unos H3MOd 31IlndOW US 6 557 077 Sheet 3 of 8 Apr 29 2003 U S Patent 914 IWALSAS LSOH 5 39V434331NI 3 11QOW WHOlIVuHVdWOO ADVLIOA INGON 22135 324106 YIMOd US 6 557 077 Sheet 4 of 8 Apr 29 2003 U S Patent vc Ov SNA 91 45 62 gt 380u1s88 N388 OWL gt adowss _ H3AMOd WALSAS LSOH 170A SAS u3MOd AgOW3W 130A Lv 31naow NOIL23 13S ADYNOS H3MOd 371000N SyOlvuvdWo5 39VIlOA ANH3IIVH U S Patent Apr 29 2003 Sheet 5 of 8 US 6 557 077 B1 69 N FROM SYSTEM FROM BBU 70 79 PFAIL 1 PFAIL 1 BBEN 0 BBEN 1 72 Se 73 _ SWITCH TO POWER FROM SYSTEM 74 SYSTEM FIG 5 POWER 4 6V YES 75 xs PFAIL 1 77 SWITCH POWER FROM BATTERY 80 POWER DOWN POWER DOWN SYSTEM IN BB MODE
5. In particular the CPU copies the configuration information stored by the cache memory or by the memory storage device to the non volatile memory device such that all memory devices now have consistent configuration information Thereafter the dirty data can be flushed from the cache memory to the memory storage device if necessary See block 62 If however the configu ration information of the cache memory does not match the configuration information of the memory storage device the CPU again issues an error message See block 64 By appropriately determining that the memory devices are similarly configured prior to attempting to flush any dirty data the computer system 14 of the present invention ensures that the dirty data is properly flushed from the cache memory 40 to a memory storage device 12 thereby pre venting loss of the data or any impairment of the integrity of the data In addition by implementing the process described above and depicted in FIG 8 the computer system permits the TMA 10 to be moved along with the memory storage device 12 such as a plurality of disk drives from one computer system to another computer system such as in instances in which the system power of the first computer system fails or the first computer system suffers some other type of hardware problem As such the dirty data can be retrieved in a reliable and repeatable fashion Many modifications and other embodiments of the inven tion will com
6. The cache memory system also includes a cache controller 160 for interacting with the central processing unit CPU 110 of the computer system and for generally controlling the operations of the cache memory system As depicted in FIG 1 the cache memory system also includes a refresh unit 177 that periodically refreshes the contents of the cache memory and a battery unit 176 for providing auxiliary power to the cache memory In order to control the manner in which the cache memory is refreshed and the manner in which auxiliary power is provided to the cache memory the cache memory system can also include a selector 180 that operates under control of the cache controller 160 As such the cache memory system can be designed such that the battery unit provides power to the cache memory if the system power supply fails or if power to the cache memory is otherwise interrupted As such the cache memory system can retain the contents of the cache memory until such time that the power failure is rectified and the computer system can again be powered on thereby permitting the contents of the cache memory to be trans ferred to main memory 120 typically a non volatile memory device for storage It is also advantageous for the cache memory 200 along with the associated battery and refresh units 176 177 collectively designated as 170 in FIG 1 to be modular so as to be moved from one computer system and installed in another computer system As such
7. device electronics IDE controller or a small computer standard interface SCSI controller After receiving the block of data the controller sends an acknowledgement of receipt to the operating sys tem Upon receiving this acknowledgement the operating system then considers the block to be safely stored in the storage device In a controller without cache memory the memory con troller transfers the data immediately to the storage device before an acknowledgement is sent back to the operating system Many higher end controllers have cache memories Cache memory is higher speed memory that stores data that has recently been retrieved from or is in the process of being transferred to a non volatile storage device thereby saving time by not requiring that the non volatile storage device be accessed if the data is needed again in the near future A memory controller also termed a caching controller that is associated with a cache memory sends an acknowledge ment to the operating system after the data is stored in the cache memory without waiting for the data to be stored in a non volatile storage device Caching controllers generally employ one of two methods to handle data that has been written to a storage device write through cache and write back cache A caching con troller employing the first method write through cache writes the block of data to two locations once the data is received that is the caching controller writes the da
8. from the cache memory to be transferred to the prior set of disk drives Alternatively if the initial test set forth in block 58 determines that the configuration information for the cache memory 40 does not match the configuration information for the non volatile memory device 16 the CPU 41 will deter mine that the TMA 10 has been moved from a first computer system to a second computer system following the powering down of the first computer system and prior to the powering up of the second computer system The CPU will then examine the memory storage device 12 in the same manner as described in conjunction with block 59 In particular in instances in which the memory storage device includes a plurality of disk drives the CPU determines if the disk drives are consistent See block 63 If the plurality of disk drives are not consistent the CPU again issues an error message See block 64 If however the plurality of disk drives are consistent the CPU determines if the configura tion information of the cache memory and the memory storage device match See block 65 If the configuration information of the cache memory and the memory storage device match such as in instances in which both the TMA and the memory storage device such as a plurality of disk drives are removed from a first computer system and installed on a second computer system the CPU restores the configuration information in the non volatile memory device 16 See block 66
9. in instances in which the cache controller 160 fails while the cache memory is dirty the battery unit can supply auxiliary power to the cache memory in order to retain the contents of the cache memory while the modular cache memory and associated battery unit US 6 557 077 B1 3 are removed from the computer system that has experienced the failure and are installed in another computer system Upon powering up the new computer system the dirty data can be flushed from the cache memory to main memory 120 such that no data is lost As a result of the removal of the cache memory from a first computer system and the installation of the cache memory in second computer system a number of problems arise in the manner in which the second computer system is initialized so as to identify the newly installed cache memory to detect if the newly installed cache memory has dirty data and to appropriately flush the dirty data to a non volatile storage device of a second computer system If the cache memory is not identified and the dirty data is not appropriately flushed data may be lost or the integrity of the data may otherwise be compromised notwithstanding removal of the cache memory from the computer system that has experienced the failure and the installation of the cache memory in a different computer system SUMMARY OF THE INVENTION A transportable memory apparatus including cache memory is provided that is capable of being removed fro
10. integrity of the data Prior to flushing the dirty data to the memory storage device however the computer system preferably ensures that the memory devices including the cache memory the memory storage device and the non volatile storage device 16 are all configured in a consistent manner In this regard a process implemented by the computer system for ensuring that the memory devices are consistently configured is depicted in FIG 8 and is typically performed following the initialization routine depicted in FIG 6 As depicted in block 58 of FIG 8 the CPU 41 initially determines if the TMA has been moved from one computer system to another In this regard the CPU obtains the configuration information from the cache memory 40 and from the non volatile storage device 16 for comparison purposes Typically this configuration information defines the manner in which the memory array is constructed If the CPU determines that the configuration information stored by the cache memory and by the non volatile storage device are the same the CPU determines that the TMA has not been moved The CPU then examines the memory storage device 12 In embodiments in which the memory storage device is comprised of a plurality of disk drives the CPU next determines if the disk drives are consistent by comparing the configuration of information stored by each disk drive See block 59 If the plurality of disk drives are not consistent the CPU issues an error
11. message See block 60 If the plurality of disks are consistent however the CPU compares the configuration information of the cache memory and the memory storage device See block 61 If the configuration information is the same the CPU can determine that the same transportable memory apparatus and the same memory storage device were previously connected to the computer system during its most recent period of operation i e prior to the last time that the computer system was powered down Since the memory devices are appropriately configured the CPU can then flush dirty data from the cache memory to the memory storage device if necessary See block 66 In this 10 15 20 25 30 35 40 45 50 55 60 65 14 regard the CPU examines the Flush flag and if the Can Flush flag is set to Valid or to TMD the CPU institutes transfer of the dirty data from cache memory to the memory storage device If the configuration information for the cache memory 40 and the memory storage device 12 are not the same however the CPU 41 can issue an error message as depicted in block 60 In this regard a user may determine that a different set of disk drives has been connected to the computer system 14 since the last time that the computer system was operated As such the user can reinstall the prior set of disk drives such that the configuration information for the memory devices will then match and permit the dirty data
12. the dirty data As such the CPU initially determines if a TMA 10 is present or alternatively whether a conventional cache memory module is present See block 94 In this regard the CPU examines the TMA channel 29 of the control bus 22 In instances in which the TMA channel is grounded the CPU will determine that a TMA is present Conversely in instances in which the TMA channel is high the CPU will determine that the TMA is not present and a conventional cache memory module is instead installed If the TMA is detected the memory controller is initialized with the SPD data previously read from the cache memory since the SPD data is considered reliable See block 95 If however the TMA is not detected and a conventional cache memory module is instead installed the memory controller is ini tialized with data typically defining the size type and other characteristics of cache memory that has been previously stored in the non volatile memory device 16 since whatever SPD data that is collected from the conventional cache memory module may not be reliable See block 96 Thereafter the CPU initializes the ECC registers maintained by the memory controller to enable error checking and correction See block 99 The CPU then verifies that the formware images in it internal read only memory ROM are correct and continues with the initialization process See block 100 During this initialization process dirty data maintained by the cache me
13. 9 2003 Sheet 8 of 8 US 6 557 077 B1 START RESTORE CONFIG IN NVRAM DRC FLUSH CACHE IF NEEDED NVC is configuration information stored in NVRAM 16 DRC is configuration information stored in Memory 40 LEGEND DKC is configuration information stored on Memory Storage 12 FIG 8 US 6 557 077 B1 1 TRANSPORTABLE MEMORY APPARATUS AND ASSOCIATED METHODS OF INITIALIZING A COMPUTER SYSTEM HAVING THE SAME FIELD OF THE INVENTION The present invention relates generally to computer that include cache memory and more particularly to a trans portable memory apparatus that includes cache memory and associated methods of initializing a computer having a transportable memory apparatus BACKGROUND OF THE INVENTION Generally computers or computer systems have associ ated devices for storing data The data may be stored on a relatively safe and recoverable non volatile storage device An example of a non volatile storage device is a hard disk drive The techniques or procedures for storing data on non volatile storage devices are well known in the art As the volume of data stored on non volatile storage devices increases however so does the concern for data integrity and reliability When a file is written to a hard disk drive the operating system transfers the data in the file generally in sections called blocks A block of data is first sent to a memory controller such as an integrated
14. United States Patent US006557077B1 12 10 Patent No US 6 557 077 B1 Ghosh et al 45 Date of Patent Apr 29 2003 54 TRANSPORTABLE MEMORY APPARATUS 5 448 719 A 9 1995 Schultz et al AND ASSOCIATED METHODS OF 5 677 890 A 10 1997 Liong et al INITIALIZING A COMPUTER SYSTEM ren d 809 aats et al HAVING THE SAME 5 982 899 11 1999 Probst 380 25 75 Inventors Sukha R Ghosh Lilburn GA US Paresh Chatterjee Fremont CA US OTHER PUBLICATIONS Stephen Scott Piper McDonough GA US Marc C Karasek Duluth GA User s Manual Mylex DBB960 Battery Backup Module US Basavaraj Gurupadappa Version 1 0 1994 Hallyal Fremont CA US cited by examiner 73 Assignee LSI Logic Corporation Milpitas CA US Primary Examiner Tuan V Thai Notice Subject to any disclaimer the term of this 74 Attorney Agent or Firm Carstens Yee amp Cahoon patent is extended or adjusted under 35 U S C 154 b by 124 days 57 transportable memory apparatus including cache memory 21 Appl No 09 612 054 and a backup battery is provided that is capable of being 22 Filed Jul 7 2000 removed from a first computer system and installed within second computer system The transportable memory 51 Int T 06 12 00 ratus includes a control bus that provides appropriate signals 52 US
15. a the TMA 10 can maintain the integrity of the data in instances in which the system power fails or the computer system has some other type of failure As such upon receiving an indication that system power has failed as indicated by PFAIL being set to 1 as depicted in box 75 the power source selector detects if the battery backup mode has been enabled by determining if 1 If battery backup mode has not been enabled thereby indicating that cache memory does not include dirty data the computer system can be powered down under the remaining system power as indicated in block 80 If however battery backup mode is enabled indicating that cache memory contains dirty data the power source selector switches the source of power to the cache memory from system power to the auxiliary power provided by the battery 23 as indicated in block 77 and then subsequently shuts down the computer system in battery backup mode as indicated in block 78 As described above the TMA 10 can be removed from a first computer system and installed in a second computer system For example in instances in which the first com puter system fails while the cache memory 40 contains dirty data the TMA and the memory storage device 12 such as one or more disk drives can be installed or connected to a second computer system such that the dirty data can be downloaded to the memory storage device thereby main taining the integrity of the data With the transportabili
16. al ports and the advanced configuration and power interface ACPI are configured in a conventional manner For example the data control mechanism such as a SCSI controller that controls the reading and writing of data to and from the memory storage device 12 is appropriately configured Thereafter the CPU 41 reads data from the cache memory 40 that defines the size of memory the type of memory the number of banks and the like See block 85 Typically this data is termed Serial Presence Defect SPD data Thereafter the CPU determines if battery backup has been enabled and or if cache memory contains dirty data See block 87 For example the CPU typically examines the BBEN channel of the control bus 22 to determine if the battery backup mode has been enabled In addition the CPU generally checks a flag that is maintained by the non volatile US 6 557 077 B1 11 memory device 16 that is set in instances in which the cache memory contains dirty data If the BBEN channel and or the flag maintained by the non volatile memory indicate that the battery backup mode has been enabled and that the cache memory contains dirty data CPU sets another flag designated GFLAG See block 91 Alternatively if the battery backup mode has not been enabled and the flag maintained by the non volatile memory does not indicate that cache memory includes dirty data the CPU clears GFLAG See block 90 Thereafter the CPU 41 initializes the memory refres
17. ation stored by the transportable memory module and the memory storage device are consistent and issuing an error message if the plurality of disks are inconsistent 6 A method according to claim 1 further comprising issuing an error message if the configuration information stored by the transportable memory module and the memory storage device are inconsistent 7 Amethod according to claim 1 wherein determining the presence of the transportable memory module comprises examining an identification channel of a control bus inter 10 15 20 25 30 35 40 45 50 55 60 65 16 connecting a transportable memory module with the first computer system which provides an indication that the transportable memory module is present 8 An apparatus for initializing a first computer system that includes a host processor and a memory storage device the method comprising first determination means for determining if a transport able memory module is present second determination means for determining if configu ration information stored by the transportable memory module and the memory storage device are consistent if a transportable memory module is present and flushing means for flushing any dirty data stored by the transportable memory module if the configuration information stored by the transportable memory mod ule and the memory storage device are consistent wherein the dirty data comprises unwritten cache data
18. by the cache memory As such if the power supply fails then the new blocks of data will be lost and non recoverable since the cache memory is volatile This loss of data is particularly problematic since the memory controller has previously sent an acknowledgement to the operating system indicating that the data was received by the storage device without provid ing any indication that the data had only been stored in cache memory Upon receiving the acknowledgment the operating system is no longer obligated to maintain the data and therefore cannot be relied upon to recover any data lost in cache memory Cache memory therefore has a central flaw When power to the caching controller fails or is interrupted for any reason the contents of the cache memory is generally lost or corrupted As the size of cache memories increase the potential for data loss also increases Numerous techniques for data recovery and data storage have been developed to overcome this problem One such attempt to resolve this problem is to have a battery backup for the cache memory One example of a conventional computer system 100 that includes a cache memory system 150 is depicted in FIG 1 The cache memory system 150 is powered by the system power supply 130 and communicates with the computer system via system bus 115 The cache memory system includes cache memory 200 typically configured as a cache array such as an Intel 21256 Dynamic Random Access Memory DRAM
19. cally reset by the host computer system the battery backup function is dis abled The setting or resetting of BBEN may be at any convenient time or pulse duration However BBEN is typically set by the host computer system when data is stored to the cache memory BBSTROBE is a stimulus from the CPU 41 to the TMA BBSTROBE acts as a clocking signal from the host computer system to the TMA to cause BBEN to be read or latched With respect to the signals provided by the TMA 10 to the host computer system 14 BBMODE 32 provides an indi cation as to whether the TMA is actually operating in a battery backup mode of operation or alternatively whether BBEN on the TMA is set or reset For example the pin to which the TMA channel is connected can also be connected via a pull up resistor to system power or some other prede termined voltage As such in the absence of a TMA such as in instances in which a conventional cache memory module is installed the pin to which the TMA channel would otherwise have been connected will have a predetermined voltage level thereby indicating that a TMA is not present Upon connecting a TMA to the host computer system such as to the interface bus 24 however the TMA will tie the channel to ground thereby providing an indication that a TMA is present As such by examining the TMA and BBMODE channels the host computer system can deter mine if a TMA is present and if so the current mode of operation of th
20. diments in which the memory storage device includes a plurality of disks the consistency of the disks can be checked prior to determining if the configura tion information stored by the transportable memory module and the memory storage device are consistent If the plural ity of disks are inconsistent an appropriate error message can be issued US 6 557 077 B1 5 According to another embodiment to the present invention a method for initializing a computer system is provided in which the memory controller is initialized in different manners depending upon the presence of a trans portable memory module or a more conventional cache memory device In this regard the method initially deter mines if cache memory contains data that is dirty If the cache memory contains data that is dirty the method deter mines if a transportable memory module is present that includes the cache memory Thereafter the memory con troller is initialized with values identifying the size and type of the cache memory At least in instances in which the cache memory contains data that is dirty the memory controller is initialized with values obtained from the cache memory if the transportable memory module is present and with values obtained from a non volatile memory device if a transport able memory module is not present Once the memory controller has been initialized dirty data stored by the cache memory can be flushed to the memory storage device If h
21. e TMA In addition to the enablement of the battery backup mode of operation provided by BBEN 30 the power source selector 20 relies upon input from the voltage computer 19 As shown in FIG 4 the voltage comparator includes a first comparator 19 for comparing the system power to predetermined minimum system threshold 34 If the system power drops below the predetermined minimum system threshold the first comparator provides a signal designated PFAIL to the power source selector and to the interface bus 24 Similarly the voltage comparator includes a second US 6 557 077 B1 9 comparator 19b for comparing the auxiliary power provided by the battery 23 to a predetermined minimum battery threshold 34 and for providing a signal 37 designated if the auxiliary power falls below the predeter mined minimum battery threshold Based upon these inputs as well as BBEN the power source selector provides the cache memory with system power or in the event that system power fails or is otherwise unavailable with auxil power from the battery In the rare event that neither system power nor auxiliary power is available the computer system will immediately initiate a power off sequence in order to avoid damaging the battery In this regard FIG 5 depicts logic implemented by the power source selector 20 As shown the host computer system 14 can be powered up in two different scenarios In the first scenario the compute
22. e presence of the transportable memory apparatus and can determine the status of the transportable memory apparatus either upon initialization of the computer system or at any time there after In this regard a method for initializing a computer system is also provided that initially determines if a transportable memory module is present such as by examining an iden tification line of the control bus interconnecting the trans portable memory module with the computer system If the transportable memory module is present it is determined if the configuration information stored by the transportable memory module and the memory storage device are con sistent If the configuration information stored by the trans portable memory module and the memory storage device are consistent the data stored by the transportable memory module is flushed to the memory storage device As such the method of this aspect of the present invention permits the transportable memory module and the memory storage device such as one or more disk drives to be transported from a first computer system to a second computer system such as in the event of a system power failure or a hardware failure in the first computer system while still facilitating the flushing of dirty data from the transportable memory module to the memory storage device once installed in the second computer system If the configuration information stored by the transportable memory module and the
23. e selector 20 to provide system power to the cache memory 40 as opposed to auxiliary power from the battery 23 as depicted in block 73 During operation of the computer system 14 the voltage comparator 19 continues to compare the system power to a predetermined minimum system threshold 34 While the voltage comparator can compare the system power to the same predetermined minimum system threshold both during initialization or powering up of the computer system and subsequently during operation of the computer system the voltage comparator can be configured such that system power is compared to a slightly lower minimum operational threshold during operation of the computer system As depicted in block 74 of FIG 5 for example the voltage comparator can compare the system power to a predeter mined minimum operational threshold of 4 6 volts If the system power falls below this predetermined minimum operational threshold the voltage comparator will again set PFAIL to 1 as shown in block 75 Once PFAIL is set the power source selector 20 will determine if the battery backup mode is enabled As described above the battery backup mode is typically enabled in instances in which cache memory 40 contains data that has not yet been stored or transferred to the memory storage device 12 By enabling the battery backup in instances in which the cache memory 10 15 20 25 30 35 40 45 50 55 60 65 10 contains dirty dat
24. e to mind to one skilled in the art to which this invention pertains having the benefit of the teachings pre US 6 557 077 B1 15 sented in the foregoing descriptions and the associated drawings Therefore it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims Although specific terms are employed herein they are used in a generic and descriptive sense only and not for purposes of limitation That which is claimed 1 A method for initializing a first computer system that includes a host processor and a memory storage device the method comprising determining if a transportable memory module is present if a transportable memory module is present determining if configuration information stored by the transportable memory module and the memory storage device are consistent and flushing any dirty data stored by the transportable memory module if the configuration information stored by the transportable memory module and the memory storage device are consistent wherein the dirty data comprises unwritten cache data 2 A method according to claim 1 further comprising if a transportable memory module is present the step of deter mining if the transportable memory module has been trans ported from a second computer system to the first computer system 3 A method accordi
25. h controller See block 92 Although not discussed in detail herein the computer system 14 also includes a memory refresh controller and associated circuitry for periodically refreshing the data stored by the cache memory 40 to further preserve the integrity of the stored data As known to those skilled in the art in instances in which the computer system is being powered up or initialized while the cache memory contains dirty data the data stored by cache memory should be refreshed sooner than instances in which cache memory does not include dirty data If the GFLAG has not been set indicating that the cache memory 40 does not contain dirty data and that battery backup mode has not been enabled the CPU 41 actually examines the cache memory to determine its size type and other related information See blocks 93 and 97 The memory controller can then be initialized with the size type and other information relating to the cache memory as shown in block 98 Although not depicted in FIG 6 the size type and other information determined during an examina tion of cache memory may be compared to the SPD data and an error message can be generated if there are significant differences therebetween In instances in which the GFLAG is set indicating that the battery backup mode is enabled and that the cache memory contains dirty data the CPU will not be able to actually examine the cache memory itself since the examination process may destroy some of
26. h the power source selector and voltage comparator can be embodied in other manners if so desired Likewise a variety of different batteries can be employed although one example of a typical battery is a Promark battery bearing part number BAT NIMH 4 8 01 As shown in FIG 4 the TMA 10 is in bi directional communications with the host computer system 14 via a control bus 22 having a plurality of information or data channels for transmitting analog or more typically digital signals either synchronously or asynchronously The control bus can interconnect the TMA and the CPU 41 either directly or indirectly For example the control bus may directly interconnect the TMA and the CPU as depicted in FIG 2 or the control bus may communicate with the CPU via an interface bus as shown in FIGS 3 and 4 The control bus 22 of the illustrated embodiment includes four data channels namely a battery backup enable channel 30 BBEN and a battery backup strobe channel 31 BBSTROBE that permit the host computer system 14 to provide signals to the TMA 10 and a battery backup mode channel 32 BBMODE and a TMA channel 29 that are provided by the TMA to the host computer system BBEN is logically set by the host computer system to enable the battery backup function of the TMA For example BBEN is typically set if cache memory 40 contains dirty data to prevent the dirty data from being lost in the event of a system power failure Conversely if BBEN is logi
27. he TMA is present the CPU 41 determines if battery backup circuitry is present as shown in block 49 As generally understood the battery backup circuitry is cir cuitry that is off board from the TMA and that permits auxiliary power to be provided to a conventional cache memory module In determining if battery backup circuitry is present for purposes of the process of FIG 7 however battery backup circuitry will only be considered to be present if both a battery 23 and the conventional battery backup circuitry are present If the battery backup circuitry is present the CPU determines if battery backup has been enabled by examining the BBMODE channel of the control bus 22 See block 50 If the battery backup mode has been enabled such as in instances in which the system power has been shut down while the cache memory 40 contains dirty data the CPU sets a flag typically designated Can Flush and stored in the non volatile storage medium 16 with a predetermined value designated TMD See block 51 By setting this flag to TMD the flag indicates that a TMA has been detected that includes a cache memory with dirty data that can be flushed If the battery backup mode has not been enabled the Flush flag will be set not to TMD but to Invalid since no dirty data was present in the cache memory at the time that the computer system was previously pow ered down or since the battery was disconnected during the prior power off sequence See bloc
28. ially in instances in which the cache memory includes dirty data In this regard the transportable memory apparatus can include a voltage comparator module that includes a first comparator for comparing the system power to the minimum system threshold If the voltage comparator determines that the system power has fallen below the minimum system threshold the voltage comparator of this embodiment will signal the power source selector The voltage computer module can also include a second comparator for comparing the auxiliary power provided by the battery to a minimum battery threshold and for signaling the power source selector if the auxiliary power does fall below the minimum battery threshold The transportable memory apparatus of this embodiment also includes a control bus for interconnecting the transport able memory apparatus with the host processor The control 10 15 20 25 35 40 45 50 55 60 65 4 bus includes a battery backup enable channel for enabling the battery to provide auxiliary power typically in instances in which the cache memory is dirty The control bus also includes an identification channel for providing an indica tion to the host controller that the transportable memory apparatus is present The control bus can further include a battery backup mode channel for indicating if the battery is currently providing auxiliary power to the cache memory As such the host processor can detect th
29. k 108 In instances in which the battery backup circuitry 1s not present the CPU 41 still determines if the cache memory 40 contains dirty data such as by examining a dirty cache flag set in the non volatile memory device 16 in instances in which the cache memory contains dirty data See block 110 If the dirty cache flag is set the CPU sets the Can Flush flag to Valid since the cache memory 40 contains dirty data that can be flushed to the memory storage device 12 See block 112 For example the computer system may have undergone a warm boot ie the user simultaneously depresses the CTRL ALT and DEL keys during a data transfer If however the dirty cache flag is not set the CPU sets the Can Flush flag to Invalid since the cache memory does not include dirty data See block 108 If the CPU 41 initially determines that the TMA 10 is not present the CPU also determines if the dirty cache flag is set as shown in block 46 If the dirty cache flag has not been set the CPU sets the Flush flag to Invalid since no dirty data remained in cache memory 40 at the time of the previous power down sequence See block 48 If however the dirty cache flag has been set the CPU determines if the US 6 557 077 B1 13 battery backup circuitry is present as shown in block 47 If the battery backup circuitry is not present the CPU sets the Can Flush flag to Valid since the computer system has undergone a warm boot during data transfer and dirt
30. m a first computer system and installed within a second com puter system According to the present invention the trans portable memory apparatus includes a control bus that provides appropriate signals such that the presence and status of the transportable memory apparatus can be detected in order to permit the computer system that includes the transportable memory apparatus to be appropriately initial ized As such methods for initializing a computer system that may include a transportable memory apparatus are also advantageously provided According to one embodiment a transportable memory apparatus capable of being relocated from a first computer system to a second computer system is provided The transportable memory apparatus includes cache memory for at least temporarily storing data transferred between a host processor and a memory storage device such as a plurality of disk drives The transportable memory apparatus also includes a battery for providing auxiliary power to the cache memory The transportable memory apparatus further includes a power source selector for selectively providing power from either a system power supply or from the battery Typically the power source selector provides the cache memory with power from the system power supply However if the power source selector detects that the system power has fallen below a minimum system threshold cache memory can be provided with auxiliary power from the battery espec
31. memory storage device are inconsistent however an error message is issued The method of this embodiment to the present invention also determines if the transportable memory module has been transported from one computer system to another computer system In this regard the method determines if the transportable memory module has been transported between computer systems by comparing the configuration information stored by the transportable memory module and the configuration information stored by the non volatile memory device of the first computer system If the configu ration information stored by the transportable memory mod ule and a non volatile memory device are different it is determined that the transportable memory module has been transported between computer systems If however the configuration information stored by the transportable memory module and the non volatile memory device match it is determined that the transportable memory module has not been transported If it is determined that the transport able memory module has been transported from one com puter system to another computer system and if the con figuration information stored by the transportable memory module and the memory storage device are consistent the configuration information of the non volatile memory device is restored by copying the configuration information of the transportable memory module to the non volatile memory device In addition in embo
32. mory will be flushed to the memory storage device 12 once the various memory devices including the cache memory the memory storage device and the non volatile memory device are determined to be consistent as described in detail below 10 15 20 25 30 35 40 45 50 55 60 65 12 In order to appropriately flush any dirty data from cache memory 40 to the memory storage device 12 the computer system 14 generally performs several additional tests as shown in FIG 7 to ensure that only valid data will be flushed While these tests can be performed following the initialization process depicted in FIG 6 these tests can also be performed during or concurrent with the initialization process if so desired While the process depicted in FIG 7 can be implemented in a number of different manners the non volatile memory device 16 of one embodiment can also store a module of code or software that is called by the CPU 41 upon powering up of the computer system that defines the process of FIG 7 as hereinafter described As such while the CPU will be described as performing many of the steps of the process of FIG 7 the CPU is typically operating under control of a software module stored by the non volatile memory device or elsewhere As depicted in FIG 7 these tests generally commence by determining if a TMA 10 is present in the same fashion as described above in conjunction with block 94 in FIG 6 See block 45 If t
33. n This invention may however be embodied in many different forms and should not be construed as limited to the embodi ments set forth herein rather these embodiments are pro vided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art Like numbers refer to like elements throughout Referring now to FIG 2 a computer system 14 including a transportable memory apparatus 10 TMA according to one advantageous embodiment of the present invention is depicted As described below the computer system operates to provide cache memory power source switching functions and memory reconfiguration functions during the activation or powering up of the computer system For example auxiliary power may be provided to the cache memory 40 in the event that the system power supply 15 should fail thereby preserving the integrity of the data stored by the cache memory If the power failure results from a disruption in the system power supply the stored data may be down loaded to a memory storage device 12 such as one or more disk drives during the next activation or power up sequence of the computer system after the disruption in the system power supply is remedied Alternatively if the power failure resulted from a failure within the computer system itself such as a hardware failure the TMA including the cache memory may be transported to another computer system The memory
34. n the memory storage device 12 When the CPU 41 references an address in memory the cache memory is first checked to determine whether the data stored at that address is stored in cache memory If cache memory contains the data requested by the CPU cache memory returns the data to the CPU 41 If cache memory does not contain the data requested by the CPU a regular memory access occurs Typical caching functions or operations are delineated in Computer Organization and Architecture by William Stallings 1990 and The Indispensible PC Hardware Book by Hans Peter Messmer Addison Wesley 1997 As depicted in FIGS 2 and 3 the TMA 10 includes cache memory 40 a power source selector 20 a voltage compara tor 19 and a battery 23 As illustrated these elements are generally separate modules but can be configured in other fashions if so desired In one embodiment the power source selector is comprised of discrete logic that receives infor mation on the state of the system power supply 15 and Switches cache memory 40 between system power and auxiliary power provided by the battery 23 when the system power supply fails Likewise the voltage comparator 19 of 10 15 20 25 30 35 40 45 50 55 60 65 8 one embodiment is comprised of discrete logic that senses both the system power level and the battery power level and provides the power source selector with comparison data As will be apparent however bot
35. ng to claim 2 wherein the first computer system also includes a non volatile memory device and wherein determining if the transportable memory module has been transported from a second com puter system to the first computer system comprises comparing configuration information stored by the trans portable memory module and the non volatile memory device determining that the transportable memory module has been transported if the configuration information stored by the transportable memory module and the non volatile memory device are different and determining that the transportable memory module has not been transported if the configuration information stored by the transportable memory module and the non volatile memory device match 4 A method according to claim 3 further comprising if the transportable memory module has been transported from second computer system to the first computer system and if the configuration information stored by the transportable memory module and the memory storage device are consistent restoring the configuration information of the non volatile memory device by copying the configuration information of the transportable memory module to the non volatile memory device 5 A method according to claim 4 wherein the memory storage device comprises a plurality of disks and wherein the method further comprises checking consistency of the plurality of disks prior to determining if the configuration inform
36. owever cache memory does not contain data that is dirty the cache memory can be examined to detect the size and type of the cache memory which values are subsequently utilized to initialize the memory controller In order to provide auxiliary power to the cache memory the computer system typically includes a battery As such cache memory may be determined to contain data that is dirty by examining the battery backup enable channel of the control bus interconnecting the memory controller and the cache memory If the battery backup enable channel indi cates that the battery is enabled cache memory will be determined to contain data that is dirty In addition a flag stored by the non volatile memory device may be utilized to indicate that cache memory contains data that is dirty As such the flag stored by the non volatile memory device may be examined to determine if the cache memory contains data that is dirty The transportable memory apparatus of the present inven tion includes cache memory and a battery for providing auxiliary power to the cache memory such that the trans portable memory apparatus can be moved from a first computer system and installed in the second computer system without losing or otherwise impairing the integrity of any data stored by the cache memory The transportable memory apparatus is also designed to provide signals indica tive of its presence and status to the host computer for use during initialization and
37. present and instructions for flushing any dirty data stored by the transportable memory module if the configuration information stored by the transportable memory mod ule and the memory storage device are consistent wherein the dirty data comprises unwritten cache data
38. r system is powered down while operating under system power and is then subse quently activated or powered up at some time later as depicted in block 68 In the other scenario the computer system is powered down while operating in battery backup mode with the auxiliary power being provided by the battery 23 and is then powered up at some later time as depicted in block 69 In either instance system power will initially be less than the predetermined minimum system threshold 34 since the system power will need some time to ramp up to the desired level such as 5 volts In instances in which the computer system is being powered up after being previously powered down while operating under system power the battery backup mode is generally not enabled as indicated by 0 in block 70 Conversely in instances in which the computer system is being powered up after previously being powered down while operating in battery backup mode the battery backup mode will be enabled as indicated by BBEN 1 in block 79 In either instance the voltage comparator 19 compares the system power to the predetermined minimum system thresh old 34 As depicted in block 71 of FIG 5 for example the predetermined minimum system threshold can be 4 7 volts Once the system power equals or exceeds the predetermined minimum system threshold the PFAIL signal provided by the voltage comparator can be reset as depicted in block 72 which in turn triggers the power sourc
39. shown Once the TMA is installed in the other computer system the TMA is designed to continue to function without loss of data stored in its memory If desired a standard cache memory module not shown may be substituted in the host computer system in place of the TMA although the host computer system will be able to detect if the TMA is present or if a standard cache memory module is present as described below As shown in FIG 2 the TMA 10 can communicate with the CPU 41 via a memory bus 21 and a control bus 22 If desired however the TMA may communicate with the host computer system via an interface bus 24 as shown in FIG 3 The interface bus 24 may be a card edge connector having either its male or female connection attached to the host computer system 14 and its mating connection attached to the TMA The interface bus provides the user with the option of inserting the TMA or inserting a standard cache memory module Either the TMA 10 or a standard cache memory module will provide the host computer system 14 with memory to store information or data during typical caching operations Caching of data is a well known procedure of temporarily storing data or information in a special memory subsystem in which frequently referenced data values are duplicated for quick access A cache memory stores the contents of fre quently accessed memory locations and the addresses where these data items are otherwise stored in main memory i e withi
40. storage device may also be connected to the other computer system such that the data stored by the cache memory may be downloaded to the memory storage device upon activating or powering up the other computer system Referring in more detail to FIG 2 the TMA 10 is shown to be connected to and in communication with a host US 6 557 077 B1 7 computer system 14 The host computer system includes a central processing unit CPU 41 The host computer system may also if desired comprise an internal or external memory storage device 12 a power supply 15 and a system bus 13 that connects the CPU 41 to the memory storage device 12 The host computer system may if desired be any computer system or controller that utilizes memory storage as discussed herein example of a host computer system is a DELL Poweredge 6300 computer system The memory storage device may if desired be one or more memory disk drives used to store data or information An example of a typical memory disk drive is a Seagate Cheetah disk drive The TMA 10 is typically connected to the host computer system 14 via an adapter slot or some other type of expan sion slot However the transportable memory module can be connected to the host computer system in other manners if 50 desired As its name suggests however the transportable memory module is transportable and may if desired be removed from the host computer system and installed in another computer system not
41. t the figures of which FIG 1 illustrates a block diagram of a transportable cache memory system of the prior art FIG 2 illustrates a block diagram of a computer system including a transportable memory module according to one embodiment of the present invention FIG 3 illustrates a block diagram of a transportable memory module interfacing with a host computer system according to one embodiment of the present invention FIG 4 illustrates a more detailed block diagram view of the transportable memory module of FIG 3 FIG 5 is a top level flow chart illustrating operations performed to switch between auxiliary power and system power FIG 6 is a flow chart illustrating the operations performed to initialize a computer system according to one embodi ment of the present invention FIG 7 is a flow chart illustrating the manner in which a flag is set during initialization operations to indicate that dirty data should be flushed from the cache memory accord ing to one embodiment of the present invention and FIG 8 is a flow chart illustrating operations performed during the initialization of a computer system to determine if the cache memory and the memory storage device are similarly configured before flushing the cache memory DETAILED DESCRIPTION OF THE INVENTION The present invention now will be described more fully hereinafter with reference to the accompanying drawings in which preferred embodiments of the invention are show
42. ta to both the cache memory and to the storage device Because the data is written to cache memory the data can be quickly accessed again if needed for later use However the data is also simultaneously stored in a safe manner in the storage device Unfortunately the time that is required to write the data from the operating system to the storage device accord ing to a write through cache method is greater than the time to write data directly to a storage device without passing through a caching controller In fact the total time to write data according to the write through cache method is equal to the time to write data to the cache memory plus the time to write data to a storage device second method write back cache reduces the time requirements of the first method by writing the block of data 10 15 20 25 30 35 40 45 50 55 60 65 2 only to the cache memory instead of to both cache memory and the storage device Therefore the total time to write data is only the time required to write data to the cache memory However the data will only be written from the cache memory to the non volatile storage device when the cache memory is full or when activity on the controller is low Unfortunately the write back cache method necessitates that the storage device will go through periods of not containing any new or updated blocks of data with the new or updated blocks of data being instead maintained
43. the like As such methods for initializing the host computer are also provided that deter mine the presence and status of a transportable memory apparatus and that flush any dirty data that has been stored by the cache memory of the transportable memory appara tus In this regard a method that insures the consistency of the configuration information of the various memory devices prior to flushing the dirty data is provided In addition a method of initializing the memory controller of a host computer system with values identifying the size and type of the cache memory is provided that determines if a trans portable memory module is present and then initializes the memory controller with values identifying the size and type of a cache memory in different manners depending upon the presence or absence of a transportable memory module As such the transportable memory apparatus and associated methods of the present invention provide for the storage and recovery of dirty data in instances in which the system power falls below a predetermined minimum level or the host computer suffers some type of hardware failure requir ing that the cache memory be transported to another com puter for recovery of the dirty data 10 15 20 25 30 35 40 45 50 55 60 65 6 BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated in the drawings in which like reference characters designate the same or similar parts throughou
44. the memory storage device are consistent 12 An apparatus according to claim 11 wherein the memory storage device comprises a plurality of disks and wherein the method further comprises means for checking consistency of the plurality of disks prior to determining if the configuration information stored by the transportable memory module and the memory storage device are consistent and means for issuing an error message if the plurality of disks are inconsistent 13 An apparatus according to claim 8 further comprising issuing an error message if the configuration information stored by the transportable memory module and the memory storage device are inconsistent 14 An apparatus according to claim 8 wherein the first determination means comprises means for examining an identification channel of a control bus interconnecting a transportable memory module with the first computer sys tem which provides an indication that the transportable memory module is present US 6 557 077 B1 17 15 computer program product in a computer readable medium for initializing a first computer system that includes a host processor and a memory storage device the method comprising instructions for determining if a transportable memory module is present instructions for determining if configuration information stored by the transportable memory module and the 18 memory storage device are consistent if a transportable memory module is
45. ty of the TMA however the computer system 14 must be espe cially designed to detect the presence of a TMA and to distinguish a conventional cache memory module and to appropriately configure the computer system depending upon the type of cache memory that is available For example the CPU 41 generally includes or is otherwise associated with a memory controller for controlling the manner in which the memory storage device cache memory and other memory devices are accessed During the initial ization process the memory controller must therefore be provided with information relating to the type and size of each memory device including cache memory In order to illustrate the process by which a computer system that may include a TMA according to the present invention is pow ered up and initialized reference is now made to FIG 6 While the process depicted in FIG 6 can be implemented in a number of different manners the computer system 14 of one embodiment includes a non volatile memory device 16 for storing a module of code or software that 15 called by the CPU 41 upon powering up of the computer system that defines the process of FIG 6 as hereinafter described As such while the CPU will be described as performing many of the steps of the process of FIG 6 the CPU is typically operating under control of a software module stored by the non volatile memory device or elsewhere As shown in block 82 the various peripheral devices seri
46. y data stored by the cache memory needs to be flushed to the memory storage device 12 See block 106 If the CPU determines that battery backup circuitry is present however the CPU determines if the battery backup mode has been enabled by examining the BBMODE channel See block 53 If the battery backup mode has not been enabled the CPU sets the Can Flush flag to Invalid since the battery 23 was apparently disconnected at some point during the power down sequence and all data has already been lost See block 54 If however the battery backup mode has been enabled the CPU determines if the PFAIL signal provided by the voltage comparator 19 indicating a failure of system power has been asserted See block 55 If PFAIL is asserted the CPU sets the Can Flush flag to Error since any data stored by the cache memory may be invalid due to power brown outs or the like See block 57 If the PFAIL signal is not asserted however the CPU sets the Flush flag to Valid to permit subsequent flushing of the dirty data maintained by the cache memory since system power was apparently shut down during a prior data transfer See block 56 By setting or resetting the Can Flush flag as described above the CPU 41 appropriately initializes the computer system 14 including the TMA 10 such that dirty data stored by the cache memory 40 will be flushed to the memory storage device 12 if the Can Flush flag is set either to Valid or TMD thereby protecting the
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