Radeon HD 7990 Review -- Part 2

[epixoip]

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.

[KT819GM]

Seeing these 6? fans and remembering citate "Biblical amount of air" I can just imagine how loud this case is. And for sure no doubt that cards stay at normal temps, you can cool down iron melting factory with setup like this. Also 4x7990 should 'eat' less electricity comparing to equivalent of 8x7970, also it makes easier to maintenance them, so seems it worth to go with these when doing insane setups.

[epixoip]

yeah, it's six 120mm fans in 3+3 configuration. they actually push less air than the previous revision which had three 120mm fans, because the previous revision allowed you to disable fan control in the bios to run the chassis fans at 100% full time. this new revision does not give you that option, which is rather disappointing. but they still get the job done.

yes, 4x 7990 uses quite a bit less power compared to 8x 7970: 1500W as opposed to 2000-2200W.

there's also a third advantage as well, and that's if you're going infiniband, you can only put 7x 7970 in each system because you have to leave a slot free for the HCA. whereas with 4x 7990 you can have infiniband plus the full 8 GPUs.

this is definitely the way forward for us.

[powderspecial600]

Would you need to leave a 2 slot gap or could you get by with just one? This way you could do more cards assuming the catalyst driver is still working with more than 8 GPUs per machine.

[epixoip]

well according to amd, you don't need to leave any gap...

http://fireuser.com/blog/8_amd_firepro_s...recision_/

but that was using firepro cards, not radeon cards, which use a different driver.

by the way, we have never been able to confirm that the driver works with more than 8 GPUs per machine. in fact, the last time we tried, it did not. do you have confirmation of this?

[powderspecial600]

I just saw once it was suppose to work with more than 8, but I haven't actually attempted to use more than 8.

[epixoip]

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

[powderspecial600]

I would be interested to know the results. That could make the Tyan chassis with 7990s ideal.(assuming you can keep them cool)

[epixoip]

it's already ideal even if you can only run 4...

[radix]

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.

So what you are saying is that its good if you throw an extra 500 bucks in case/fan behind it.