Folding Hardware Questions

[drewdsterling]

Hey, when GPUs on the secondary markets become extremely cheap when mining slows down can you fold with 19 GPUS on one board?  I saw the Asus B250 mining expert board and thought it would be extremely efficient to fold with.  My main question is does Folding at Home support 19 GPUs per board?  If so I would love to see LTT do an episode of this on that crazy rig that they have.  Thank you for all of the responses in advance!

[alextheaverage]

I don't think Folding has a limit of gpu's per board but you'd need mining specific cards to populate all slots according to the mining video Linus put out.  

[drewdsterling]

Gotcha is there any folding members that have a setup like this? 

[Ithanul]

Also, mining boards limit down to 1x.  That will hurt your PPD output.

 

The most GPUs I seen folding on one board is around five to six, but that is rare since you start losing PCI-E bandwidth.  Typically, the most I see other folders do on one board is four GPUs.

[Uzume]

Depending on the type of GPU in use, I have seen each GPU utilise between 0.2 to 0.33 CPU threads on Seti@Home (so likely similar for folding). That is why you never let the Boinc client saturate your CPU or or you will starve out your GPUs.

 

If you haven't gimped out a mining rig with the weakest possible CPU then there shouldn't be much of an issue. But having said that, it isn't unusual in mining rig building to do exactly that.

[alextheaverage]

5 hours ago, zzrhardy said:

Depending on the type of GPU in use, I have seen each GPU utilise between 0.2 to 0.33 CPU threads on Seti@Home (so likely similar for folding). That is why you never let the Boinc client saturate your CPU or or you will starve out your GPUs.

 

If you haven't gimped out a mining rig with the weakest possible CPU then there shouldn't be much of an issue. But having said that, it isn't unusual in mining rig building to do exactly that.

Now that you mention CPU I'm pretty sure that Folding@home uses one logical core per GPU, so four GPUs would need a minimum of four CPU threads.  A thirteen GPU folding rig would need an AMD 1700 just to run.

[foldinghomealone]

13 hours ago, alextheaverage said:

Now that you mention CPU I'm pretty sure that Folding@home uses one logical core per GPU, so four GPUs would need a minimum of four CPU threads.  A thirteen GPU folding rig would need an AMD 1700 just to run.

Normally I would agree to that statement. (Normally means in a setup where GPUs are connected to x8 or x16.)

 

As Ithanul stated with 19 GPUs they are connected to x1 which slows down modern GPUs significantly. I'm not sure if makes things much slower when you share one thread with several GPUs. 

Furthermore, many miners use AMD GPUs which tend not to need 1 thread per GPU compared to NVs.

 

However, checking current GPU prices makes me scream and I'm not sure if second hand GPUs become 'extremely cheap' in the near future. 

 

 

[alextheaverage]

2 hours ago, foldinghomealone said:

Normally I would agree to that statement. (Normally means in a setup where GPUs are connected to x8 or x16.)

 

As Ithanul stated with 19 GPUs they are connected to x1 which slows down modern GPUs significantly. I'm not sure if makes things much slower when you share one thread with several GPUs. 

Furthermore, many miners use AMD GPUs which tend not to need 1 thread per GPU compared to NVs.

 

However, checking current GPU prices makes me scream and I'm not sure if second hand GPUs become 'extremely cheap' in the near future. 

 

 

For Folding though?  I haven't significantly folding in the past year or two since Folding is crash happy with Nvidia/AMD mixed systems but even when I had two R9 290's folding I could only use two CPU cores to CPU fold.  I do agree with your 8x/16x statement though.  That will be a bigger issue way before you get to CPU thread issues.

[GloriousPain]

There's a req of 1 thread/GPU... plus PCIE lanes will be an issue; if you really are serious about this; I'd suggest getting an old server system; like a Dual Socket LGA 1366 w/ 2x Xeon X5650s  with a few PCIE slots and get a splitting riser board if you can find onelike a 1Port->4 port setup or something close.

[Ithanul]

On 2/2/2018 at 8:57 PM, alextheaverage said:

For Folding though?  I haven't significantly folding in the past year or two since Folding is crash happy with Nvidia/AMD mixed systems but even when I had two R9 290's folding I could only use two CPU cores to CPU fold.  I do agree with your 8x/16x statement though.  That will be a bigger issue way before you get to CPU thread issues.

Yes, the bandwidth will hurt.  A few of the big folders on OCN did a test a year or more ago (would have to hunt out the thread).  Was determined at most, going down to x8 was not super bad, but anything below made noticeable decrease in points.  I ran my GTX980Tis in x8 and was out doing 1070s.  So, at least x8 is not bad to run with for F@H.

 

The common rule for Nvidia GPUs is one CPU logical core per card with one core for the OS because of the driver overhead.  AMD cards can get away with less.  Right now though, Nvidia GPUs are still top king in F@H output with current WU cores.  Though, from the few folders I know that run AMD cards have seen an increase in point output with the latest WU cores.