From: Simon Thorpe Newsgroups: comp.parallel.pvm Subject: Multiprocessor PCI boards Date: Thu, 03 Sep 1998 13:09:11 +0100 Organization: CNRS Message-Id: <35EE86DC.2DFE@cerco.ups-tlse.fr> Reply-To: thorpe@cerco.ups-tlse.fr Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Hi, Over the past few months I have been in discussion with Neil Carson from Causality Ltd. http://www.causality.com/ in the UK about the possibility of developping hardware for doing neural network simulations. Right now, the project is looking very promising, and Neil has said that he would be happy to go ahead and build a first batch of 25 boards as soon as he can be reasonably confident that there will be enough buyers. I myself will be buying 8-10 boards, but we need a few other interested people to get the project off the ground. I was wondering whether anyone on the comp-neuro mailing list might be interested. Briefly, what we are proposing is the following. The basic board will be a standard PCI board that could be used in PCs, Macs or indeed any other computer with PCI slots in it. Each board would be fitted with 6 processor modules, three on each side, which would plug into standard SODIMM memory slots (Small Outline Dual In-Line Memory Modules), the same type of slots that are used for memory expansion on laptop computers. Each of these daughter boards would have a StrongARM SA-110 micro-processor, a Digital 21285-A PCI bridge circuit, and 32 Mbytes of SDRAM. In effect, each board would be a computer in its own right, and would run a version of Unix (Linux or NetBSD). It would also have an IP address, allowing messages to be sent efficiently via the PCI bus from processor to processor. Neil and the other programmers at Causality will look after the message passing mechanisms, probably using I20 protocols (if you know what that is). In our case, we want to use these boards to run a parallel version of SpikeNET, our asynchronous spiking neuronal network simulator. It turns out that this particular program would parallelise very nicely on such a system, because the communication bandwidth between processors is kept very low. If you're interested in SpikeNET, just let me know - we're seriously thinking about making the program available to whoever wants to use it. But in fact, the same hardware could also be used for any sort of parallel program that could be run using PVM or MPI message passing protocols. There are some limitations though. The StrongARM SA-110 doesn't have a floating point unit, but as long as you only want to do integer calculations, it goes like a rocket. Our own software (which is integer only) runs as fast on the StrongARM as on a Pentium II of the same clock speed. This is really impressive, since the StrongARM doesn't have a second level cache (unlike the Pentium II) and the code has (as yet) not been optimised for the StrongARM at all. The reasons for choosing the StrongARM are pretty straightforward. It is very small, doesn't get hot (< I Watt) and is cheap. This means that it becomes perfectly feasible to imagine packing large numbers of StrongARMs in a very small space without having to worry about overheating (imagine trying to do the same thing with Pentium IIs). In addition, although the future of StrongARM was once in doubt (it was co-developped by Digital and Advanced Risc Machines), it has now been bought up by Intel who have recently announced that they will be investing heavilly in StrongARM development. See http://developer.intel.com/design/strong/ for details. The current top-of-the-range StrongARM runs at 233 MHz, and this is what Neil Carson is proposing to use in this first batch. However, in the not to distant future there will be 400 MHz StrongARMs with 100 MHz SDRAM memory busses. And there will be a new StrongARM processor (the SA-1500) which will have a separate floating point unit for multimedia operations. One of the nice features of this daughter board arrangement is that it would be pretty simple and cost effective to do a new batch of boards using whatever the best technology is at that moment. Another advantage of using this sort of parallel hardware is that even last years technology will still be useful to you - not like conventional PCs where you feel that you have to buy a new computer every six months if you don't want to be obsolete. So, what about prices you may be saying. Well, if you are interested it should be possible to do such a board for 1200 pounds ($2000) on this first run. Each board would only take one PCI slot, so with four free PCI slots you could put up to 24 processors in a single PC! If we can round up enough interested people, we should be able to get the boards done in about 2 months. Please note that I am not personally going to making any money on this, and Causality are only expecting to break even on it. However, both Neil and I are confident that this could be a really promising approach - we just need to get enough support to get the ball rolling. Obviously, the more people that are interested, the cheaper it gets.... If you want more information, don't hesitate to contact either me at thorpe@cerco.ups-tlse.fr or Neil at neil@causality.com. Best wishes Simon Thorpe