8x7990 Power Requirements
Hello all,

I was poking around trying to figure out the actual power requirements for a 7990, and the best I can come up with is a single 7990 has a maximum load power requirement of between 350 and 400 watts (I believe it requires a minimum of 35A on the +12v rail..)

This puts an 8x7990 (actually 2 systems with 4 in each), at 2800-3200w for just the graphics cards. If I include efficiency calculations, I'm actually looking at 3080-3520w for just the cards.

Is this accurate, or am I missing something?

Hello r0dn3y,

First, welcome to the forums. Currently I have one similar system running with 4x 7990.

I'm using 2x 1600 watt LEPA power supply's per machine. I noticed under full load on 1x 1600 watt the system became unstable / consuming too much on peak. Each 7990 has two power connectors so what I did was using a connector from supply 1 and one from supply 2. This way the power draw is shared over the two PSU's and the system is stable.

You should take a note that you need very good cooling to keep those dual gpu cards cool enough. I had to build a small cool-rig to keep this system cool enough to run 24/7. See: http://www.youtube.com/watch?v=HiWRt2aL9tg

I ordered another 4x 7990's for my second machine to VCL them together, will share the power consumptions once all is pieced together in the next couple of weeks. Currently this machine (depending on what tasks it runs) has the following consuptions:

Idle: ~ 350 watt @ 230V
Full load: ~ 1400-1700 watt @ 230V
I decided to back off from the 4 in each box down to 3, to keep the power requirements into a single 1600w LEPA. Specs for the new build are below.

Case: Cooler Master HAF XB LAN Box
CPU: Core i7-3970X
MB: Asus Rampage IV Extreme
GPU: 3x XFX Radeon HD 7990
RAM: 32GB Ballistix Sport XT (4x8GB)
SSD: 2x Samsung 840 EVO 750GB (In my box) 2x 250GB of the same (in my assistants box)
PSU: LEPA G-Series 1600W

Both are doubling as primary workstations.
Will post pictures of the setup and the hardware when I get it in.
And what about cooling?
The CPUs are being cooled by Corsair Hydros (the 2x140mm rad). For the GPUs, initially the cooling will just be the case fans until I figure out how much additional cooling I actually need. Little bit of trial and error. The room the boxes are going to be in is kept at about 68 degrees, so I don't forsee their being much of an issue as long as the hot air from the GPUs is vented out of the case well. That is actually why I picked the Lan Box, as it appears to have a mesh top for venting. If not, I'll be digging out the dremel. :-)

I'm planning on the cooling not really being completely adequate under full load, and I'll probably end up having to build an LC loop combined with a chiller instead of a rad to handle the load from the GPUs.

BTW, Thats an awesome cool-rig.
Chiller for ~1125W of TDP? Electricity cost to feed compressor only will be high. That's if I correctly understood what cooling solution you want to do.
Cost to feed all of this equipment will be pretty high. The chillers I'm looking at pull combined about 1kw, that roughly means $101 a month.

Course, my electric bill for this equipment alone will probably be around that.
(08-21-2013, 03:42 PM)r0dn3y Wrote: Case: Cooler Master HAF XB LAN Box

You're not even going to be able to cool a single 7990 in that chassis, let alone four.

Maybe you should read my reviews of the 7990 in the hardware forum.
I use 1 of those cards in a cooler master CM690-II case with 5 fans taking care of separate room temp air intake and hot air exhaust and I can't get gpu 0 below 98 Celsius and gpu1 not below 88 Celsius. those cards get so darn hot!

As for the power usage the card consumes up to 475 watt.