Chimera 3.2 - Docket Alarm
Contents
1. himera 3 2 http web archi ve org web 20020927070327 http vasc ri cmu edwold_ 7 Chimera 3 2 A real time operating system developed at CMU which is far better than anything else you ll find on the market Table of Contents Overview Examples Cool Stuff References See Also VASC Contact History Overview The Chimera 3 2 Real Time Operating System has its own HTML page which more than adequately covers what it does and how to use it Let me therefore take this opportunity to answer the question Why use Chimera instead of VxWorks Besides the fact that it has a wonderful graphical interface called Onika I mean Here s what Chimera inventor David B Stewart has to say on the subject Frequently Asked Questions about Chimera vs VxWorks Q What are the similarities and differences between the VxWorks and Chimera real time kernels A As with most other commercial real time operating systems VxWorks only provides a basic real time kernel which gives you task management low overhead context switching and local semaphores static highest priority first scheduling and an interface to program the hardware timers for periodic events Chimera provides an extended real time kernel In addition to all the basic functions that VxWorks provides it also gives you both static and dynamic real time scheduling virtual timers which eliminate the need to explicitly program hardware timers the novel deadline failur2. have priorities Chimera s message passing is a multiprocessor mechanism Chimera s kernel does not have built in message passing The timings are for local messages when using the multiprocessor message passing mechanism in the Chimera communication library Q With VxWorks an RTPU can communicate directly with a different computer system on the network Can I do anything like that in Chimera considering you don t yet support ethernet in the backplane A Yes you can Chimera allows communication by an RTPU over ethernet with other systems by using the host workstation s ethernet An easy to use interface is a front end to the awkward socket interface required to send and receive messages over ethernet Going through the host workstation is completely transparent to the programmer With this setup you have not lost any performance as compared to VxWorks which does support an ethernet in the backplane in VxWorks one RTPU still has to communicate to the RTPU hosting the ethernet However the Chimera design remains consistent with the global local operating system decomposition where the local operating system performs all the real time stuff and the global operating system takes care of the non real time or soft real time stuff like the file system workstation graphics and networking Q Chimera 3 0 is advertised as a real time operating system for reconfigurable sensor based control systems Why is it preferred to use Chimera
3. highest priority first scheduling and an interface to program the hardware timers for periodic events Chimera provides an extended real time kernel In addition to all the basic functions that VxWorks provides it also gives you both static and dynamic real time scheduling virtual timers which eliminate the need to explicitly program hardware timers the novel deadline failure handling and global error handling mechanisms and two level device driver support Q Chimera claims it is a multiprocessor operating system while VxWorks only claims it has multiprocessor support What is the difference A VxWorks is only a single processor operating system with multiprocessor extensions Those Page 1 of 7 10 7 2013 3 16 PM Chimera 3 2 http web archive org web 20020927070327 hup vase ri cmu cdw old_ 2017 extensions involve networking multiple VxWorks systems over the backplane using the TCP IP protocol The only difference is that the communication medium is the backplane and not ethernet This setup is no more a multiprocessor setup than two Sun workstations on the same local area network Chimera is a multiprocessor operating system because the kernels on multiple Real Time Processing Units RTPUs i e single board computers can communicate with each other via Chimera s high performance system level communication called express mail Without such kernel level interprocessor communication an operating system cannot make interp
4. cs etc These programs appear to run on the RTPU but in fact execute on the host workstation but the results are sent to the RTPU s stdout and input is received from the RTPU s stdin Special Purpose Processors SPP Chimera treats special purpose processors such as floating point Page 3 of 7 10 7 2013 3 16 PM Chimera 3 2 hitp web archi ve org web 20020927070327 hup vasc ri cmm edwold_ 4of7 accelerators LISP machines and image processors as slaves which execute a short efficient non preemptive executive A programming running under Chimera can then execute a procedure remotely The SPP drivers automatically handle the communication and synchronization between the RTPU and the SPP VxWorks has no equivalent interfaces Interrupts Chimera provides a hardware indepedent interface for generating and handling both VMEbus and mailbox interrupts Chimera also gives you 256 mailbox interrupts per RTPU even if the RTPU only supports one or two mailbox interrupts as is the case with most RTPUs VxWorks does not provide any special support for interrupts you are at the mercy of whatever the hardware gives you and must program the hardware using non portable code Q How does the hardware support compare between Chimera and VxWorks Chimera has concentrated on providing as much functionality as possible along a single line of RTPUs initially However nothing precludes poviding support for multiple RTPU s We expec
5. e handling and global error handling mechanisms and two level device driver support Q Chimera claims it is a multiprocessor operating system while VxWof ABB v ROY G BIV multiprocessor support What is the difference Trial IPR2013 00063 ABB EXHIBIT 1100 A VxWorks is only a single processor operating system with multiproces Page 1 of 7 10 7 2013 3 16 PM himera 3 2 U http web archi ve org web 20020927070327 http vasc ri cmu edwold_ 7 Chimera 3 2 A real time operating system developed at CMU which is far better than anything else you ll find on the market Table of Contents Overview Examples Cool Stuff References See Also VASC Contact History Overview The Chimera 3 2 Real Time Operating System has its own HTML page which more than adequately covers what it does and how to use it Let me therefore take this opportunity to answer the question Why use Chimera instead of VxWorks Besides the fact that it has a wonderful graphical interface called Onika I mean Here s what Chimera inventor David B Stewart has to say on the subject Frequently Asked Questions about Chimera vs VxWorks Q What are the similarities and differences between the VxWorks and Chimera real time kernels A As with most other commercial real time operating systems VxWorks only provides a basic real time kernel which gives you task management low overhead context switching and local semaphores static
6. ere published comparing a few commercial RTOS A Topper A computing architecture for a multiple robot controller M S Thesis McGill University Those same benchmarks were executed on Chimera following are the results NOTE The authors are providing these results without any explicit or implied warranties Page 4 of 7 10 7 2013 3 16 P http web archi ve org web 20020927070327 http vasc ri cmu edwold_ himera 3 2 Queue Fill 46 26 140 20 66 Queue Drain 43 29 132 22 GRA Queue Fill Drain 91 59 278 44w 120 Queue Fill Urgent 47 27 170 72 67 Alternate Queue F D 238 252 867 371 570 Allocate Memory 40 27 57 68 42 Deallocate Memory 38 33 20 83 36 7 VxWorks does not support message passing These times are from simulating message passing through the use of shared memory Note the times above are as quoted in the thesis This must have been an older version of VxWorks since VxWorks now has a message passing mechanism described in their sales brochures The numbers given in the sales brochure are the following e msgQSend no tasks pending 77 o task pending 129 o queue full 68 e msgQReceive message available 73 o message unavailable 65 Based on these numbers we would expect the Queue Fill to be 77 Queue Drain to be 73 Queue Fill Drain to be 150 and Alternate Queue F D to be at least 450 It is unclear whether Queue Fill Urgent is possible as the sales brochure does not specify if messages can
7. his predictable real time communication mechanism allows Chimera to communicate with other subsystems which may or may not be running Chimera or to communicate with intelligent memory mapped I O devices or special purpose processors The code for the mechanism is extremely portable so that it can be compiled to execute on any non Chimera platform VxWorks does not provide any such mechanisms Host Workstation Interface Chimera allows processes on the host workstation to attach to the real time environment by appearing to the RTPUs as just another RTPU This allows communication between the host and RTPUs to occur in the same transparent manner that RTPUs communicate with each other For example a graphics application on the host can display real time data by reading from a shared memory segment on one of the RTPUs In VxWorks any host to RTPU communication must be done through the ethernet which is slow less predictable and much more difficult to program Transparent Host Procedure Calls RTPUs can execute remote procedure calls on the host workstation either to execute some non real time code or to obtain information that is otherwise not available on the RTPUs For example RTPUs have a physical clock but they don t have a time of day clock So calling the function gettimeofday is automatically transfered into a remote procedure call and the time of day from the host is returned An RTPU can also execute programs like Is ema
8. inter kernel communication in Chimera all the VMEbus address offsets can be calculated automatically during the initialization of the shared memory and all operations are transparent to which processor the segment is actually on In VxWorks addresses of shared memory segments must be hard coded into user s code with the offsets with are RTPU dependent also added manually This makes the code non portable and difficult to maintain if the hardware configurations are changed as each hardware change requires a modification of the source code The only reason this is available in VxWorks is because the VMEbus allows it Le VxWorks makes no special provisions for global shared memory In Chimera no such modifications are required and the same executable can be run even if the base addresses of any of the RTPUs in the system are changed Spin Locks This is a front end to the lowest level of interprocessor communication using the atomic test and set TAS instructions VxWorks lets you use the TAS instructions but do not provide a convenient front end for using them and automatically timing out if the lock cannot be obtained Page 2 of 7 10 7 2013 3 16 P himera 3 2 http web archi ve org web 20020927070327 http vasc ri cmu edw old_ f7 Remote Semaphores In addition to local semaphores Chimera provides remote semaphores which allow tasks on all RTPUs to use a semaphore VxWorks has only local semaphores interrupts must ex
9. itutions and other projects Why should we break this trend and use Chimera A Unfortunately this is a myth that far too many people believe Just because multiple projects centers use the same operating system does not mean that they will have any code that is reusable or compatible between them It is a standard software architecture and not the operating system that provides compatibility between multiple projects Since VxWorks does not provide support for any specific software architecture every project uses its own architecture and hence despite using the same operating system the applications are not at all compatible Here is an example of a similar situation Consider two projects each using Sun SPARC stations with SunOS 4 0 One of them uses SunView while the other is uses X windows You develop a graphics application for X windows It is NOT compatible with the other project using SunView even though both are running under the same operating system However a third project is using a DEC PMAX running Ultrix 3 2 and X windows The graphics application DOES run on the DEC even though it is using a completely different hardware architecture and a completely different operating system The reason is they are both using the X11R5 standard protocol which is a standard software architecture for window applications When developing applications under Chimera we recommend that the reconfigurable software framework be used so that m
10. n run Chimera on any given machine chim Cool Stuff I really can t mention them all here it s best for you to check out the Chimera 3 2 Real Time Operating System page There s a huge manual on line which gives programming examples function definitions and much more References The Onika User s Manual the Chimera 3 2 User s Manual See Also Chimera VxWorks Onika History 10 14 94 Created by Matt Gertz This page has been accessed times Page 7 of 7 7 10 7 2013 3 16 PM
11. over VxWorks for reconfigurable systems A In order for a software module to be reconfigurable it must satisfy the two following conditions 1 the module is independent of target hardware 2 the module is independent of target application Because multiprocessor operations on VxWorks are not transparent and VxWorks does not provide any generic interfaces to special purpose processors or sensors and actuators the first condition Page 5 of 7 10 7 2013 3 16 PM Chimera 3 2 htp web archi ve org web 20020927070327 hup vasc ri cmu eduold_ 6of7 above is violated All Chimera multiprocessor communication is hardware independent Chimera also has two level device driver support for I O devices and sensor actuator interfaces and a generic SPP interface providing additional hardware independence to non general purpose CPU hardware Chimera has many tools built in to the operating system to support the reconfigurable software framework being developed at CMU The state variable table mechanism configuration file reading utility and subsystem task control mechanisms are but a sample of those tools which simplify the task of writing reconfigurable software modules which are independent of the target application Since VxWorks does not have any such tools it is easier to satisfy the second condition using Chimera than it is when using VxWorks Q Our managers say that we should use VxWorks because it would keep us compatible with other inst
12. plicitly be sent by the user if multiprocessor synchronization is required Prioritized Message Passing Chimera s message passing is multiprocessor Any task on any RTPU can send or receive a message to from any queue Messages can be retrieved either first in first out last in first out or highest priority first In VxWorks message passing is local to an RTPU To send a message to a remote RTPU either sockets must be used or a communications layer must implement the message passing on top of shared memory with interrupts for signaling It is not clear from VxWorks literature but queues might only be first in first out Global State Variable Table Chimera provides this communication mechanism for predictable real time communication and making efficient use of the VMEbus bandwidth One global table exists and every task which attaches to the table has a local copy of the parts of the table it needs Updates of the local and global tables are done periodically and predictably This is a must communication mechanism for developing reconfigurable software VxWorks does not provide anything comparable Subsystem Multiprocessor Task Control Chimera allows a task on one RTPU to control tasks i e spawn block etc on multiple RTPUs This is another feature required when developing reconfigurable software which must execute on multiple processors VxWorks does not provide anything comparable Triple Buffer Communication Mechanism T
13. rocessor communication transparent to the user s programs running on each RTPU and limit both the types of higher level communication mechanisms that can be designed and their performance Q We have written a communications layer above VxWorks Will this work with Chimera A Because Chimera is a multiprocessor operating system there is no need for such a communications layer Almost anyone using multiple processors and VxWorks is required to write such a layer because of VxWorks lack of multiprocessor support In Chimera all the communication mechanisms are built in to the operating system so you don t have to write them Because they are built in everyone uses the same ones as opposed to what happens today with projects using VxWorks where every project or institution has their own custom layer thus limiting any potential software reuse or technology transfer Q What are the communication mechanisms available in Chimera and how does each compare to VxWorks A Here is a quick rundown of most of them Express Mail this is a high performance real time non blocking communication mechnism between the kernels on each RTPU and the host workstation This mechanism allows the other interprocessor communication and synchronization mechanism to operate transparently across multiple processors Global Shared Memory tasks can dynamically create and attach to shared memory on any processor and access that shared memory Because of the
14. t that this will happen in due time At present though VxWorks supports several different models of RTPUs Chimera provides several device drivers for off the shelf I O hardware such as DAC ADC parallel I O and serial O VxWorks does not provide such drivers Chimera also provides device drivers for some special purpose processors allowing user s to access the SPP s through the Chimera generic SPP interface VxWorks does not have any such drivers Several SPP hardware vendors do sell VxWorks drivers however those drivers always have custom interfaces thus making them non portable with the interfaces of other SPPs Q How does the technical support for Chimera software compare to the support given for VxWorks by Wind River Systems Chimera H did not have any official support however those using Chimera II can usually get an answer or bug fixes within a couple of days directly from the authors With Chimera 3 0 similar support will be available from the authors However when the software is commercialized it will be possible to buy a software support contract in which case there will be official support Q What is the performance of Chimera vs other RTOS A The biggest strength of Chimera is in all the added features which are not available in other real time operating systems RTOS However despite the additional functionality Chimera s performance is at par with VxWorks and other RTOS Some benchmarks for real time kernels w
15. ultiple applications at multiple institutions are compatible with each other If one project uses the framework and the other doesn t then you won t have compatibility between those projects The advantage of Chimera over VxWorks in this case is that Chimera gives you all the tools necessary to easily and quickly implement an application based on the reconfigurable software framework VxWorks on the other hand has no corresponding software architecture and no corresponding tools Every project must then develop their own architecture and tools and hence application development takes a lot more time and the application is not compatible with the applications in other projects or centers In summary maintaining consistency between multiple project is NOT a function of the operating system it is a function of the software architecture Examples Page 6 of 7 10 7 2013 3 16 P chimera 3 2 http web archi ve org web 20020927070327 http vasc ri cmu edu old_ For visual examples check out the Onika HTML page If you want to use Chimera here s what you need to do to your paths and environment setenv CHIMERA_ARCH SARCH setenv CHIMBRA_DIR chimera chim 3 2 setenv CHIMERA_CONPIG CHIMERA_DIR config chimera config HOST setenv CHIMERA_LOCAL your_top_directory_of_Chimera_software setpath PATH i CHIMERA_DIR SCHIMERA_ARCH bin Then it s just a matter of entering on a machine which runs Chimera remember only one one user at a time ca
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