Reality check on CPU vs GPU folding.

[bdwilson]

Example system:

i5 3570K @ 4 Ghz - ~9-10K PPD.
7950 @ 950 Mhz ~ 109-110K PPD

The used 7950 actually costs LESS than a used i5 chip, but gets 10X as many points.

Now points don't matter to me in theory. My real question is, do the points being given in the example above reflect the value of the science being done? I've heard that CPU's run different work than GPUs, and I'm curious if the "value" given to CPU units has been adjusted to reflect the actual value to the project, or could they possibly be undervalued compared to the points given to GPU units? This is an important question, because if the unique WU's going to CPUs are accurately valued by the developers compared to GPU units, is it even worth it to fold on a newer CPU given the point difference? For the same price, instead of getting a newer i5 system with DDR3 and a moderate video card, I could get a used Core 2 Duo PC for $100-ish total and throw in a high end video card capable of getting 400,000+ ppd. The systems will cost roughly the same, and the sacrifice made in CPU points (i5 vs Core 2 Duo) will be more than made up for by the boost given by the video card.

What do yall say?

[7im]

Every PC that can fold on a GPU always comes with a CPU that can fold. You might as well be folding on both, even if you skimp on the PC specs to afford a faster GPU. It's not uncommon to build a low end bare bones PC with one or more higher end GPUs when only using the system for folding.

But the performance pendulum swings back and forth. CPUs were the top dog for a long time when multiple cores came out. Then GPUs have taken the lead for a while now. Next year when Intel comes out with a 512 bit wide FPU compared to today's 128 and 256 bit wide FPUs, the CPU is then (theoretically) capable if processing 2-4 times the SIMD instructions per clock cycle as the current CPUs (assuming fah will upgrade their FAHCores to support this). This would make CPUs very competitive on a performance per watt comparison with GPUs.

Ask this question today, GPUs win. Ask the question tomorrow, the answer may be different. Caveat Folder.

[Nathan_P]

I will make 2 responses to this, a cpu or 2 or 4 was quite happy folding a WU with over 1m atoms, I haven't yet seen a gpu WU with anything like that many atoms. Given the equal pay for equals work statements that have been made, the gpu WU must be 8 times harder to fold than an 81xx WU.

@OP - if you are just starting out afresh - don't bother cpu folding, get the cheapest machine that will run a Maxwell gpu, install a card to suit your budget and let it run. Its different if you have existing folding kit

[bdwilson]

@OP - if you are just starting out afresh - don't bother cpu folding, get the cheapest machine that will run a Maxwell gpu, install a card to suit your budget and let it run. Its different if you have existing folding kit

I'm not folding now, but was just thinking of doing this.

Complete Core 2 Duo PC (minus OS, which I have), ($50): http://www.ebay.com/itm/S124-DELL-OPTIP ... 1797215932
Power supply upgrade ($40): http://www.ebay.com/itm/750W-Gaming-120 ... 1229901254

So that's $90 for the system, and every other penny will be spent on the best video card I can cram in there. Would there be anything wrong with a new folder building several systems like this?

[Napoleon]

1GB system RAM sounds small to me. I'd venture to say that 2GB is minimum, 4GB is comfortable and 8GB is more or less futureproof. Having said that, you probably get by with 1GB and a frugal Linux distro, but some of the newer and bigger projects such as 9704 - no can do. And P10492 is even bigger...

[bdwilson]

Napoleon, I am just going to GPU fold on this system. I was planning to let the cpu/ram focus exclusively on running the GPU folder as fast as possible.

[Napoleon]

GPU FahCores pass data back and forth between the GPU and system RAM all the time. The (intermediate) results are stored in system RAM, and if it's a big simulation with lots of atoms, that requires a lot of system RAM. 9704 and 10492 are GPU projects with lots of atoms, and therefore have system RAM requirements approaching those of the now defunct CPU BigAdv projects.

p9704 is now available for beta testing on windows. This requires a 64 bit version of windows and >= 2GB system ram. The large ram usage mandates a 64 bit core. In future core21 projects, there will be both a 64 bit and 32 bit core

Granted, most currently running GPU projects have much smaller system RAM requirements, but the fact remains, there already are a couple of GPU projects where 1GB or even 2GB system RAM isn't enough. I do not know whether they're just exceptions to the rule or a sign of things to come.

On a side note, amount of VRAM is hardly ever an issue. Even big projects like 9704 and 10492 only hold a fraction of the entire dataset in VRAM at any given time, a few hundred megabytes or so.

To recap, most likely you can run GPU folding on a setup with 1GB system RAM (for quite some time still). Nevertheless, even now it limits the selection of WUs you'll be able to fold to some extent. You wouldn't get assigned any of the existing GPU FahCore 0x21 WUs. If it so happens that all of the future 0x21 projects will be as big as the aforementioned two examples - or even bigger - you'll be stuck with 0x17 and 0x18 work.

In the worst case scenario, investing in a couple of those low end setups to see how it goes isn't a huge loss, but if you're going to buy a truckload of them to start a GPU farm... well, I'd be a bit wary in your shoes. Furthermore, CPU and PCIE speeds have some effect on GPU folding speed, so you might not be able to squeeze out every last drop of performance from a top notch GPU.

[bdwilson]

Thanks, that's just the sort of useful information I was hoping to get.

[Nathan_P]

@OP - if you are just starting out afresh - don't bother cpu folding, get the cheapest machine that will run a Maxwell gpu, install a card to suit your budget and let it run. Its different if you have existing folding kit

I'm not folding now, but was just thinking of doing this.

Complete Core 2 Duo PC (minus OS, which I have), ($50): http://www.ebay.com/itm/S124-DELL-OPTIP ... 1797215932
Power supply upgrade ($40): http://www.ebay.com/itm/750W-Gaming-120 ... 1229901254

So that's $90 for the system, and every other penny will be spent on the best video card I can cram in there. Would there be anything wrong with a new folder building several systems like this?

The idea is sound - I wouldn't go anywhere near that psu though, if you are building a rig that you want to last and be efficient and not blow up when you load it to 50-60% of its PSU's capacity choose a name brand psu like seasonic, corsair, evga etc. It will be more expensive but you will be thankful in the long run. My personal recommendation at the moment would be a seasonic 750 or corsair ax760