Ello all, Sorry to be a pain in the jacksey with this, but I ran some of the numbers from the F@H feature in Issue 70, and thought "There must be some other, better way to get max output per £ and W than 4 GTX295s... Plus, that's mighty pricey!" So, after a fair amount of number-crunching, I think I've got it. (Don't laugh... ready?) 4 nVidia GTS250s in an MSI K92A Platinum. Yes, the re-badged 9800GTX+ actually HAS a use! Going off the numbers in the CPC Folding feature, accounting for processors' power consumption and PSU efficiency, 2 of these graphics cards will run from a 15A 12V rail, meaning that with PCI splitters, the whole shebang, including processor, can be run from a 500-550W PSU with ease, giving about 22k ppd, and (here's the clever bit) buying the 4 GPUs, K92A Plat, Athlon X2 7750+, 2GB of RAM, and a Seagate Barracuda 80GB IDE drive, costs £535 delivered from Scan (I priced it up at eBuyer and Novatech, but couldn't get lower than £575 at Nova, and eBuyer only had the 7850, so £600+ there) I'm fine for a PSU, PCI power splitters, screws and elbow grease, but I do have 3 questions: 1) 2GB or 4GB of RAM? (FYI, I have access to 64-bit versions of XP, so no problem there) - I'd assume 2, since Folding's not demanding and it's XP, but thought it best to check. 2) Is there a drastic difference in the ppd of the 512MB and 1GB versions of the GTS250, and is it worth an extra £10ish per card (there'll be no gaming)? 3) What about a case? Ideally, I'd like to keep the budget low on this, but I know it's not vital. However, were I to put it in a case, what do you reckon would do the job best? I know phoenicis used an Antec 902 for his 4 GTX295s, but witht he 250s, I wouldn't need quite as much cooling power, and I don't fancy spending £100 for a grand ppd gain of zero. Many thanks for any input, guys. Will
Sounds good. I have a K92A Platinum with three 9800gt cards in it. Saspro has several. He wrote part of the magazine article, if I recall correctly. Lots of the others know more than me, but I think they are asleep, except Unicorn. I use a Maplin A02GN case, which looks similar to an Antec 300, but has a 22 cm fan on the side. If you are putting 4 graphics cards in a case, you should also have three 12 cm fans. I think 2 GB is plenty of RAM for a folding PC. I don't think graphics memory size matters for folding at the moment, this might change in the future if bigger molecules are modeled. I would be nervous of using less than a 800 wat PSU for that set up, but that is just me. I am no great expert.
Thanks for the feedback, boss. Much appreciated! As it turns out, I'll actually be using a 700W PSU, but the cards themselves use something like 89W each (I had to pull some mad extrapolation using the figures from the CPC article to get there, but I did in the end, thankfully!), which is 7.42A each, so 2 can run from a 15A rail (in theory - I'd like to have some spare to play with, so I'm going for 18A rails - more than enough!) Does the Maplin case have room for 4 dual-slot cards (ie 8 PCI expansion slots)? Cheers, Will
Sounds like a good system. The only cases with 8x pci brackets at the back are the big armoursuit from Lian Li and the Antec 900-2. Of those the antec is about a quarter of the price of the lian li so gets my vote. The other option is no case and stick it on a bit of wood. The K9A2 is a great board I have a few of them, 2GB RAM will be fine. The 512MB cards will be all you need as memory doesn't (currently) cause any issues (the WU's are tiny). Go for a branded PSU and try to get as many pci-e connectors as you can (up to the number you need of course), splitters work but if you need to use 2 of them then you need 4x rails with molex on to split it properly (although I have run 4x 8800GT's on a 600w supply before with only 2x pci-e plugs & 2x splitters). Make sure you get something like a freezer 64 for the cpu as there will be a lot of heat in that case.
I have K9A2 boards, with only 2GB RAM and 4 9800GX2 cards. I get 'out of memory' messages when I try to run 2 instances of SMP folding under VMware, but then I'm only using 32 bit Windows XP. But otherwise 8 GPU clients and Windows SMP no problem with 2GB.
A big thumbs up for the Lian Li PC-P80 Armorsuit. A beautiful case, great engineering, and light weight aluminium. The 900-2 wins on price! (Not so sure about the 4/1 ratio. The 900-2 is typically 90 quid and the PC-P80, £220/230.)
Thanks for all the help, guys. I'm quite happy at my thoughts on this one, although I've still got no word on whether there's a significant difference in performance between the 512MB and 1GB versions of the GTS250. If there is, I may as well splurge the extra 40-ish quid, and get the 1GB versions. However, if it's a case of "Nope", or "Not really", I'll leave it be. Cheers, guys! Will EDIT: Would it be possible to cut into the Maplin case to add some room for the 4th graphics card to blow air out the back? I'm thinking a quick 30 seconds with a pair of tin snips might sort the jobbie out.
Maplin A02GN case No, the 7 slots take up all the room between the motherboard i/o sockets and the bottom of the case. http://homepage.ntlworld.com/zath.ras/pic/wilma_01.jpg This is a picture of Wilma, which has a Maplin A02GN case, K9A2 motherboard, three 8800gt cards.
