OTOY Forums

Hi
currently i am using two gtx 780 cards in my workstation. Another one is on the way. The system is build around a supermicro x9dai with two xeon E5 2650v2 and 64 GB RAM. The PSU is an Enermax Platimax 1000W.

I measured the power consumption while rendering. With 2 GTX 780, the system is consuming ~450w. Prime95 (max heat & power consumption) pulls ~500w off the wall. Is this PSU good enough for installing another one? (assuming that GPUs and CPUs are not going to have full load at the same time)

Thanks for your thoughts.

You might be fine with Your PSU, as it is quite capable. Keeping in mind 83A rating. Each 780 eats up to 250W & from 12V is ~21A. So.. 63 for GPUs & the rest (20A) for the system..- might come working, but You're on the edge (depends what other hardware You have). However I think it will not have enough connectors (8 & 6 pin) for GPUs, so You'll have to combine those from Molex or Sata (if You have those free =)

I would try to power up the system as they even claim PSU is going to handle 1100W load, but on the long run I would look for one more PSU to connect helping, 'cos You might face stability issues =)

I have one connector left with 6+8 pin. I think i'll try it out.
Another thought was to put the third GTX in one of my other workstations and use network rendering when v 2.0 finally arrives.
I thought someone has a similar setup running with that PSU.

based on the power draw numbers you posted above you have heaps of head room...

Your power stats are a little misleading: 450w rendering is likely very low cpu load, and larger GPU load: 340w (2x170w) for the 780's, and then the remaining for system (low load).

While prime95 is likely max system power draw, and minimal/no gpu load/draw.

I would try to get an off-the-wall reading while voxellizing a scene - this is likely to be your biggest real world load.
Alternatively get the 780's rendering then start your cpu's going on a Mentalray render or something - that way you will get max load of everything

At CUDA rendering, that might work. I had an 800W one (Fractal Design) that wasn't up to even feeding two 780 Ti OCs for gaming .... for rendering it had worked. My new Seasonic 860W handles both cards without issue. There are spikes in certain game scenes, that can go over the PSU, despite much milder average consumption seen in the card tests (which are always lower than maker specs). I remember having owned a card/PSU where everything worked but only one game scene would crash it all. I find 1000W very edge limit for 3 780s if they cause a peak somewhere .. but you may have it working fine. Also: At a certain amount of cards, they draw too much sometimes over the PCI slots, despite having additionall connects for power. The it will fail unless you can supply the PCI bus with extra power on your motherboard (my asus ws-e can do that)... but maybe that's only for 4 GPUs, as I have four x16 slots and it is intended at such powerusers ... 3 cards may be fine without that?

I've installed the three cards for about two weeks now and it works fine. Measured output is ~650W while rendering a heavy scene.

Yea, it really seems to me that the total power draw stated on NVIDIA's card specs really are max, not typically what you will see when under load. When I added a GTX 770 4GB Classified, it has (2) 8-pin connectors and a 250W total power draw rating. But when rendering in Octane, it only added ~115W to my total system consumption. There are occasional spikes, but still not 250W worth. I think they might include extra headroom for those who are raising the clock speed and voltage.

When rendering via Octane I get 70% TDP on any card I use.
This must mean that rendering doesn't use card as games do for example.
But I'll check TDP on 780Ti while gaming today. Just curious.

Maybe something for you to compare; I have two Titans and one gtx275 running on 950W.
Greetz,

slepy8 wrote:When rendering via Octane I get 70% TDP on any card I use.
This must mean that rendering doesn't use card as games do for example.
But I'll check TDP on 780Ti while gaming today. Just curious.

That would be interesting....

I really don't get how the 'compute' focussed applications like Octane do not actually draw more power than games(?). Perhaps is all about the memory, which possibly does not work as hard in Octane after scene load, while games are probably very dependent on active swapping etc with mem. Duno, just speculating...

Seeker