George's dream build - Page 15

Mark Rose · 2016-07-31, 22:42

Quote:

Originally Posted by masser

Given the power/space limitiations, what kind of GPUs could you add to these rigs?

That depends...

I had four boards stacked, but instead I have them lying on a shelf side by side now for better cooling. I could easily add graphics cards to all of them, but not on a single power supply.

Prime95 · 2016-08-01, 00:36

Quote:

Originally Posted by masser

Given the power/space limitiations, what kind of GPUs could you add to these rigs?

The whole point of my rig is to make the most cost efficient LL testing solution. GPUs of any kind would not fit my goal.

However, if you wanted to add cost efficient TF compute power then a GPU makes sense. I haven't done the research, but I don't think the picoPSUs could support a GPU -- it depends on how much power the GPU draws from the motherboard slot vs. power drawn from the separate 12V cables. If you'll do that research, then we might be able to figure out exactly what is possible.

After the power distribution is worked out, then you'd need to purchase an adequate power supply, find splitter cables for the 12V feeds to the GPU, make sure none of your 12V lines are overloaded, work out an optional enclosure with fans to push all that heat away.

endless mike · 2016-08-01, 02:43

Looking at my stack, (posted earlier in this thread) there's really not any room to stick a GPU into any of the boards. Not to mention heat issues that would arise. The CPUs are currently running in the mid 60 degree range, with both sides off the case.

Quote:

Originally Posted by masser

Given the power/space limitiations, what kind of GPUs could you add to these rigs?

bgbeuning · 2016-08-01, 15:45

The PCI spec allows a card to draw up to 75W from the motherboard PCI 16x connector.
(The only reason I know this is from the recent AMD RX 480 issue.)
The 6 wire ATX connector for a GPU is also limited to 75W but people routinely exceed that.

So given the i5-6500 and H110 uses 60W, we need a PicoPSU over 135W
assuming the ATX power for the GPU comes direct from the main PSU.

masser · 2016-08-05, 04:05

Quote:

Originally Posted by Prime95

However, if you wanted to add cost efficient TF compute power then a GPU makes sense. I haven't done the research, but I don't think the picoPSUs could support a GPU -- it depends on how much power the GPU draws from the motherboard slot vs. power drawn from the separate 12V cables. If you'll do that research, then we might be able to figure out exactly what is possible.

I took a stab at this. I considered two problems:

1. Add cost-efficient GPUs to the 90W picoPSU systems you've built.

The most cost efficient purchase I could find with a TDP less than 52W (the upper bound would be very risky, I know) is:

GT 730, GhzD/D: 57.6, TDP: 25 W, Cost: $52.99

I recently purchased one of these for an energy efficient build; it only pulls 15 W (measured on a kill-a-watt) while running mfaktc. I used two metrics to make the cost efficient determination:

GVR3 = (3*GhzD/D)/(Cost+3*TDP) and

GVR4 = (4*GhzD/D)/(Cost+4*TDP).

2. What if George buys the 160W picoPSU for his next mobo/cpu/mem purchase, in order to keep the form factor, but increase the possibilities for the expansion slot on the mobo? Here I found two compelling purchases:

a. "Should be safe" Consider GPU with TDP <= 69 W. The most cost efficient purchase here that I could find:

GTX 750TI, GhzD/D: 139.7, TDP: 60W, Cost: $104.99

b. "Probably safe" Consider GPU with TDP <= 101 W. The most cost efficient purchase in this range:

GTX 950 (75W model), GhzD/D: 192.3, TDP: 75W, Cost: $144.95

Without more data, this is mostly idle speculation. It would be extremely useful to have actual wattage measurements for GPUs running mfaktc/mfakto. It would also be nice to know if anyone has tried to drive one of the listed GPUs with a picoPSU. I think the GT730 would be safe in George's current rig.

As for the cooling/noise issues, I will leave that as an exercise for the interested reader...

Prime95 · 2016-09-04, 18:59

Quote:

Originally Posted by endless mike

Had my first issue between one and two days ago based on last check in date.
Attachment 14541
Note the melted white connector and wire insulation.
Attachment 14542

I just had the exact same problem

I thought it would be safe to run 3 boards off this one connector since different 12V lines from the PSU power each board.

Any recommendations on the best way to avoid this in the future? I have two CPUs out of commission until I fix this.

endless mike · 2016-09-04, 20:28

Quote:

Originally Posted by Prime95

I just had the exact same problem

I thought it would be safe to run 3 boards off this one connector since different 12V lines from the PSU power each board.

Any recommendations on the best way to avoid this in the future? I have two CPUs out of commission until I fix this.

I ended up rebuilding the connectors.
New PCIE ends from eBay (here)
14 gage solid core wire from the local hardware store instead of the 18 gage stranded core speaker wire.
Reused the barrel connector end from the original adapters.

I also only put two CPUs per adaptor instead of the three that they originally had. My PSU has enough PCI-E power connectors to make splitting them up possible.

I don't know that the heavier gage wire was absolutely necessary, or if just running only two CPUs per adaptor was all I really needed to do.

I rebuilt them in the second week of July, and they've been fine since (knock on wood).

bgbeuning · 2016-09-05, 01:07

My system has 4 of those connectors.
It has been running 6 months without a problem.
One feels a little warm but the rest are cool.

The power wiring is taking up lots of space in my 4U case,
so I was thinking of redoing the wiring using

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

so you are giving me a second reason to redo the wiring.

cybergreg · 2016-12-22, 12:40

I have read through the first 5 pages of this one, so don't know yet if anyone has suggested this, or even if it will work. A good friend of mine at Southampton University had this go viral a while back: https://www.southampton.ac.uk/~sjc/raspberrypi/ I have absolutely no idea whether you could run Prime95 on this or not or if you could whether it would be worth it or not. But I thought it looked cool

Mark Rose · 2016-12-22, 16:26

Quote:

Originally Posted by cybergreg

I have read through the first 5 pages of this one, so don't know yet if anyone has suggested this, or even if it will work. A good friend of mine at Southampton University had this go viral a while back: https://www.southampton.ac.uk/~sjc/raspberrypi/ I have absolutely no idea whether you could run Prime95 on this or not or if you could whether it would be worth it or not. But I thought it looked cool

Raspberries are basically useless/terribly inefficient for what we do.

Mark Rose · 2017-03-24, 15:32

Has anyone tried splitting the ATX power connector to more than 4 systems?

I'm only using ~320 watts on my 650 watt power supply and I'm tempted to squeeze another two systems in.

I'm using the EVGA GQ 650W (fantastic power supply, btw).

2016-09-05, 01:07	#162
bgbeuning Dec 2014 2²×3²×7 Posts	melting My system has 4 of those connectors. It has been running 6 months without a problem. One feels a little warm but the rest are cool. The power wiring is taking up lots of space in my 4U case, so I was thinking of redoing the wiring using https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 so you are giving me a second reason to redo the wiring.

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2016-08-01, 15:45	#158
bgbeuning Dec 2014 252₁₀ Posts	The PCI spec allows a card to draw up to 75W from the motherboard PCI 16x connector. (The only reason I know this is from the recent AMD RX 480 issue.) The 6 wire ATX connector for a GPU is also limited to 75W but people routinely exceed that. So given the i5-6500 and H110 uses 60W, we need a PicoPSU over 135W assuming the ATX power for the GPU comes direct from the main PSU.

2016-12-22, 12:40	#163
cybergreg Dec 2016 1010₂ Posts	I have read through the first 5 pages of this one, so don't know yet if anyone has suggested this, or even if it will work. A good friend of mine at Southampton University had this go viral a while back: https://www.southampton.ac.uk/~sjc/raspberrypi/ I have absolutely no idea whether you could run Prime95 on this or not or if you could whether it would be worth it or not. But I thought it looked cool

2017-03-24, 15:32	#165
Mark Rose "/X\(‘-‘)/X\" Jan 2013 29·101 Posts	Has anyone tried splitting the ATX power connector to more than 4 systems? I'm only using ~320 watts on my 650 watt power supply and I'm tempted to squeeze another two systems in. I'm using the EVGA GQ 650W (fantastic power supply, btw).