GPU folding on a budget!

OK, following a slight delay in my folding plans I now have more time to think about setting up a low-power, low-budget folding rig. I'm looking (I think) at 3 basic options:

1) fiddle with existing Socket A set up.
I have an aging socket A PC that is about to be retired as my primary office PC, and I'm loathe to just let it go. Research has pointed me towards AMD Geode NX processors, which are basically very low power Athlon XPs, and I've found I can pick one up for < £30 (off that much lo(v|ath)ed auction site). I could then add a new(ish) AGP graphics card - e.g. HD4650 - and do GPU folding on that. The TDP for the Geode NX is only 25W, so even fully loaded the power draw shouldn't be too horrific.

2) mini-itx + PCI GPU
There's plenty of cheapish low power Atom / Via / Geode LX / etc mini-itx boards out there, all armed with PCIc slots. Now, I know PCI is massively limited in terms of bandwidth, but I was wondering how bad the limit was, and whether it would bottleneck a PCI graphics card (e.g. HD2400) during GPU folding.

3) new low power build
Given how taken I am with my Sempron 140, I could build a new machine based on a cheap 780V/G motherboard + Sempron 140 and fold on the IGP. I assume this would work, since the IGP is basically just a 2400 with no dedicated RAM.

Now, I think pretty obviously the first option would give me the greatest folding power, but it would also draw the most power and I really don't want my electricity bill going through the roof!

The second option appeals aggressively, mostly because I think I like the idea of being able to fold on a tiny little Pico-PSU powered box. With spare bits of kit I've already got lying aorund this shouldn't set me back any more than option 1, and while the throughput won't be nearly as good, it should draw significantly less power - in the region of half, if I'm any judge.

Option 3 would have to wait as I don't have the cash for a new build, but is probably the safest in terms of usable technology. It'd also leave me the option of getting a more powerful GFX card later (on a more sensible PCIe interface) to increase the folding speed. But where's te fun in building anothrer eneric made range PC, huh? ;)

So, any thoughts? What would you do in my situation? (All three is not an acceptable answer, btw ;) ). Will PCI bottleneck GPU folding (even on a measly 42GFlop 2400)? Does that matter, given the inherent coolness of a tiny itx folding machine?

scaryjim...you realise the importance of a good cpu to gpu folding?

4850
\/
PCIe x16
\/
phenom II x2 @ 3.9

= around 70% cpu usage

seriously? What does the cpu do in all that, marshall all the work units etc to the gpu? I'm surprised it's that heavily CPU dependant! Then again, it's been a couple of year since I last even vaguely looked at folding, and I haven't investigated the GPU client that much - I'm just aware that it exists and is more efficient than the CPU client!

I think that definitely puts the kaibosh on option 1 anyway - there's no way my old Athlon XP could push enough work to a 4650, by the sounds of it! I guess the theory is to keep the system basically in balance then? Presumably using a 2400 PCI I wouldn't need as powerful a CPU as the GPU would be crunching the numbers a lot slower?

*sigh* looks like it's back to the drawing board for me... :(

it will be futile tbh. dual core athlon and a radeon 3850/3870 second hand from somewhere would be worthwhile though- a hell of a lot of grunt for bargain prices, you could probably put a cpu/mobo/ram/gup/hdd/case/psu and have chage from £100

but then.. quite a few phenom 1\'s for sale at knockdown prices, stick one of those in, two 3850\'s and weeeee you are able to run 2x gpu clients and an multi-core client one one comp

its addictive - thats why i stopped it :laugh:

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Originally Posted by MadduckUK

its addictive - thats why i stopped it :laugh:

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Argh! I've got an addictive personality and I'm really interested now!!!!

I've actually just picked up a dual-core Athlon and an SLI mobo off the for sale's here with a view to folding (although I was considering making that my principle office machine so my 8800GTX doesn't eat the leccy bill when I'm just writing a static html page!) - how do ATI and NVidia GPUs compare in terms of output? I believe folding doesn't run under SLI anyway, and you have to use the 2 GPUs separately? Does one archtitecure perform better than the other?

i think nvidia gpu's put out a significant amount more than ati gpu's. a good nvidia card to choose is either the 384Mb 9600gso ot the 512Mb nividia 8800gt

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Originally Posted by scaryjim

how do ATI and NVidia GPUs compare in terms of output? I believe folding doesn't run under SLI anyway, and you have to use the 2 GPUs separately? Does one archtitecure perform better than the other?

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and the other half of the and cause it seems Al has past experience of the rest - yup, you cant add another and double the speed, you have to double the number of work units you are doing simultaneously . which for all intents and purposes is the same so that's ok. remember though that that will use 2x the processor, so you DO want a quad if you are going for 2 GPU clients... because then you can run a cpu client on the spare cores:)

Cool, thanks for the input guys :) Guess I'll have to wait until I can afford a couple of 9600GT / 9800GT Eco cards to start really crunching through the WUs. Presumably if I was content to just run the 2 GPU clients I'd be OK with a reasonable dual-core on that kind of setup for now (I can always add a 45W Athlon II X4 later - assuming they ever come out).

I reckon I might still have a pop at making a ridiculous mini-itx folding box just for a laugh - that and the excuse to buy an Antec Mini Skeleton ;)