PSU Loading and Bandwidth with multiple PSU's

Tom M
Tom M
Joined: 2 Feb 06
Posts: 2,223
Credit: 3,746,030,347
RAC: 5,791,462
Topic 227227

Hi,

I am looking at using multiple PSU's to segment my power loads on a mining-like multiple gpu system.  Or chasing down a 2000 watt PSU (which might mean I can't use my current house wiring).

Anyway.

It seems like the highest continuous load you want on a PSU is 70% of its rating.  For example 1600 x 0.7 = 1120 watts.  850 x 0.7 = 595 watts.

A YouTube video made a solid case for all power for a GPU coming from the same PSU.

So I guess the only question I have left is should I load 3 rtx 3080 ti's directly onto the MB where they will have slightly higher PCIe bandwidth (4x, 3x, 2x) compared to 1x slots that I power the GPU "risers" externally.  Or should I run the current setup of 2 3080 ti and 1 3080? And power the 3rd rtx 3080 ti with a separate PSU / riser-card like solution?

I have demonstrated the possibility of running 5 gpus on this rig.  So I know I am going to end up with the "last two" gpu's on a separate PSU.  Right now that combination would look like either an Rtx 3080 ti or Rtx 3080 with an Gt 1080 (for 5 gpus).

Power limits are 300 watts maximum and as far as I can tell both the 3080 ti's and the 3080 are pulling a full 300 watts.

I am running Einstein at Home exclusively on the target system.  So there is less or no impact between using 1x and 4x solutions (apparently).

Respectfully,

Tom M

 

 

 

 

A proud member of the O.F.A. (Old Farts Association)

My other CPU is a Ryzen 3950x

mikey
mikey
Joined: 22 Jan 05
Posts: 8,569
Credit: 686,797,475
RAC: 2,582,384

Tom M wrote:Hi,I am

Tom M wrote:

Hi,

I am looking at using multiple PSU's to segment my power loads on a mining-like multiple gpu system.  Or chasing down a 2000 watt PSU (which might mean I can't use my current house wiring).

Anyway.

It seems like the highest continuous load you want on a PSU is 70% of its rating.  For example 1600 x 0.7 = 1120 watts.  850 x 0.7 = 595 watts.

A YouTube video made a solid case for all power for a GPU coming from the same PSU.

So I guess the only question I have left is should I load 3 rtx 3080 ti's directly onto the MB where they will have slightly higher PCIe bandwidth (4x, 3x, 2x) compared to 1x slots that I power the GPU "risers" externally.  Or should I run the current setup of 2 3080 ti and 1 3080? And power the 3rd rtx 3080 ti with a separate PSU / riser-card like solution?

I have demonstrated the possibility of running 5 gpus on this rig.  So I know I am going to end up with the "last two" gpu's on a separate PSU.  Right now that combination would look like either an Rtx 3080 ti or Rtx 3080 with an Gt 1080 (for 5 gpus).

Power limits are 300 watts maximum and as far as I can tell both the 3080 ti's and the 3080 are pulling a full 300 watts.

I am running Einstein at Home exclusively on the target system.  So there is less or no impact between using 1x and 4x solutions (apparently).

Respectfully, Tom M 

There was research done at Seti showing that not much benefit was gained when using more than a 4x gpu slot for a gpu but below a 4x slot there was a loss of RAC, I seem to remember it was from the lack of bandwidth a 1x or 2x slot provides versus a 4x and above slot. Moderator Gary Roberts may have alot of info in this area for Einstein as he uses alot of different pc's with the gpu's all set  up nearly identically. You could probably test this yourself with your current machine and slots using identical gpu's in the various pci-e slots for a period of time.

A guy on my Team, who's no longer crunching due to a stroke, often used a 2nd psu outside the case just for the gpu's so he didn't have to buy huge psu's, it worked great for him.

Zalster
Zalster
Joined: 26 Nov 13
Posts: 3,117
Credit: 4,050,672,230
RAC: 141,101

Tom,  Ask Keith about

Tom, 

Ask Keith about this. I seem to remember you need to power up both PSU at the same time. So there needed to be some sort of control switch to power them both. The issue was if 1 powered up and the other didn't then you could experience some sort of overload or short which is what you definitely don't want.  The band width issue was more of a Seti project than Einstein due to the high efficency of the app.  Now that Petri is working on increasing the speed of the app, I don't know what the lower level of bandwidth that is acceptable. As you know, depending on what kind of MB you have the slot bandwidth will go down with new GPU. I'm still running older X99ew-s which are 8x on all 4 slots but i'm currently only running 2.  This has to do with the built in chip that supplements the 3,4 pci slots.  You are running a mining rig board?  I'm guessing the PCI is probably pretty low to begin with.

 

Z

Tom M
Tom M
Joined: 2 Feb 06
Posts: 2,223
Credit: 3,746,030,347
RAC: 5,791,462

After wobbling around I think

After wobbling around I think I will go ahead and install my other 1600 watt PSU on the production box. Found the original PSU adapter to allow 2 or 3 psu to synchronize.

The swapped rtx3080 ti just showed up. So outside of getting it to room temperature all I have to do is a bit of screwing and unscrewing.

And play with my cat.

Tom M

A proud member of the O.F.A. (Old Farts Association)

My other CPU is a Ryzen 3950x

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