Radeon HD 7990 Review -- Part 2

[epixoip]

yeah, they're good to go when you have proper airflow. two or three Delta AFB1212GHE or QFR1212GHE would do fine in the right case. so $50-$120.

[zarabatana]

naw. when 13.1 was released and removed the Xorg requirement, we theorized that more than 8 GPUs might work since Xorg was what was crashing when we tried to use more than 8 GPUs. however we've not actually tried it. but, i just might try it today

So, did you tried it?
Thank you for your time and patience.

[forumhero]

great info, thx for sharing. i'm also curious about the, more than 8gpu, results as well

[epixoip]

i need the 64-bit bios, which is not publicly available, to try it. board will not POST with more than 8 GPUs. i think d3ad0ne knows who to get it from, so i'll ask him.

[Rolf]

What were the temps like? I'll tell you, friends: 75C all day long.

What about FurMark?

Neat review.
Whose hand is that in the photo?

[msalman]

which main board is that
and win support x8?

[epixoip]

What about FurMark?
Neat review.
Whose hand is that in the photo?

We're running Linux on these, so I have not tried FurMark. But I cannot think of anything that is more stressful than lite or bitcoin mining, as both hammer the shit out of the ALUs.

That's Bitweasil's hand in the photo

[powderspecial600]

We got a few more Tyan chassis in today, so we were finally able to test multiple 7990s in a proper server chassis.

Our setup was simply 4x XFX FX-799A-XNF9 in a Tyan B7015F77V4R, leaving a 2-slot gap in between each card.




These cards are advertised as being clocked at 950 Mhz core / 1375 Mhz memory, but they actually come out of the box running at 1000 Mhz core / 1500 Mhz memory.

In the Tyan chassis, the cards idle at 27C - 30C. Nice and chilly. This is opposed to 40C at idle in the desktop chassis. So we're off to a good start already -- or are we?

As I mentioned in my previous review, the 7990 only works with Catalyst 13.6 beta. However, I only tested a single card in my last review. I expected everything to be the same with multiple cards, just as it's been for recent previous versions of Catalyst. So you can imagine my surprise when I fired up lite, and saw that it was only using one GPU. You know what this means...

That's right folks, we're back to using dummy plugs!

For some reason, AMD regressed to requiring a monitor be hooked up to each card in order to use it for compute in 13.6. Hopefully this will once again be resolved in 13.7, but for now, I'm glad I kept all my dummy plugs after AMD promised they would no longer be necessary. Filthy liars.

After digging through a stack of boxes to find my vast dummy plug collection, I popped one onto each card and restarted X. Bingo, we now have compute on all 8 GPUs.

So here's the part you've all been waiting for...

What is the speed like? Exactly the same as 8x 7970 Ghz Edition.

What were the temps like? I'll tell you, friends: 75C all day long.

Well not exactly, but damn close. Under full load I saw temps as low as 60C, and a couple times the cards hit 80C, but for the most part, they stayed right in the mid 70s. Which is perfect, that's right where we were hoping to be. Suck it, radix!

And mind you these cards are overclocked, the temps would be even more acceptable if we ran them at the stock 7970 clocks.

So in summary,

7990 + desktop = bad
7990 + high-end server = fantastic

And don't forget your dummy plugs.

We are debating this same config tyan chassis / 4 - 7990s. I am curious what is your ambient air temp where this machine operates to get them to operate at 75C. Also do both the front and back GPUs on the 7990 operate at 75 or does one run hotter? In my experience one seems to run about 5 degrees warmer or so that the other.

[epixoip]

ambient is around 23C. no, they both run at the same temp. but the gpu that drives the display, even when just sitting at xdm, is always hotter.

[powderspecial600]

Thanks, I am guessing mine second runs a bit hotter since I have the GPUs installed vertically vs horizontally. I am thinking the hot air from the first one is going straight up into the second one.