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Radeon HD 7990 Review
06-17-2013, 07:12 AM
Post: #1
Exclamation Radeon HD 7990 Review
Just unboxed an XFX Radeon R7990 and decided to try it out with lite.

First impression, the card is extremely sturdy and well-built. The shroud is all metal. The heatsink and fan setup appear adequate at first glance. The card also has a metal backplate, which we have not yet seen from AMD with this generation of cards. The card is very long, seems longer than a 6990, though I didn't have one handy for comparison.

I installed it in a mid-size ATX case with quiet fans. The case fans do not push very much air, as they are designed for silent operation rather than performance. The 7990 is the only GPU in this case. I had to remove some hard drive caddies to make it fit, because it's so long.

This system is running Ubuntu 12.04 desktop with Catalyst 13.4. Immediate problem: this card does not work with 13.4. Catalyst 13.4 reports that no supported devices are installed, and xorg defaults to the vesa driver.

It is now working with 13.6 beta. This driver reports itself as "13.101," I'm not sure why. But the card is now working. I can also see that this card comes out of the box clocked at 1000 Mhz, instead of the advertised 950 Mhz. I also noticed that the memory is well overclocked as well, running at 1500 Mhz instead of 1375 Mhz.

Running lite 0.15 with --force, GPU performance is exactly to be expected. Same speed as 2x 7970. However we have an immediate problem with heat.

Even though this is a reference design card, it dissipates heat like an OEM cooler. The fans vent the air inside the chassis, not out the back of the card. There is no airflow coming out the back of the card at all, it is all coming out of the top of the card. Since this case does not have very powerful fans, the fans are not able to exhaust all the hot air the GPUs are pushing into the case.

Running lite, temps were around 86C for the GPU driving the display, and 80C for the second GPU. However, when the benchmark got to MD4. the temp on both GPUs spiked up over 90C. The GPU driving the 1080p display got up to 95C before I killed it.

I set the clocks at what would be a normal stock clock for a 7970 (non-Ghz edition), which is 950/1375, and manually set the fans to 100%. It ran about 6C cooler for all the algorithms, until we got to MD4 again, which made it spike up to 92C.

I dropped the core down to 850 Mhz and benchmarked just MD4 for 300 seconds, and while it stayed around 86C for most of the run, by the end it had reached 90C.

I think that if this card were used in a chassis which had sufficient airflow, such as a server chassis or open-air system, then it would not be too much of a problem cooling these cards. But it seems the largest reason AMD is able to claim that these cards are so quiet is because it's relying on the chassis fans to cool the cards. So I would not advise one to use this card in a desktop chassis at all, unless your desktop is populated with Delta fans.

Next week I will have the opportunity to install multiple 7990s into a proper server chassis with powerful fans, and I will let you know how the 7990 fares under those conditions.
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06-17-2013, 09:39 AM
Post: #2
RE: Radeon HD 7990 Review
(06-17-2013 07:12 AM)epixoip Wrote:  Next week I will have the opportunity to install multiple 7990s into a proper server chassis with powerful fans, and I will let you know how the 7990 fares under those conditions.

remember to make some pictures Wink
whats the price you payed for the 7990 ?
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06-17-2013, 10:14 AM
Post: #3
RE: Radeon HD 7990 Review
$1050 - $1100 each.
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06-17-2013, 12:37 PM
Post: #4
RE: Radeon HD 7990 Review
What its speed on MD5? Somewhere at 18000 MH/s?
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06-17-2013, 12:51 PM
Post: #5
RE: Radeon HD 7990 Review
yeah, ~ 17.7 GH/s at 1000 Mhz. same speed as 2x 7970 at the same clock.

the heatsink on the 7990 is really nice, I think the problem is a combination of the slow fans and the vent design. the fans spin at a very low rpm and do not push much air at all. and the other problem is that it exhausts into the chassis, instead of out the back. that's always a really bad idea.

however, this cooler was originally designed for the FirePro S10000, and therefore originally designed with server use in mind. so i'm really hoping that they will do fine in a Tyan chassis. i assume that they will since amd recently built a Tyan box populated with eight S10000 cards with this exact cooling solution. but we'll find out when the Tyan chassis for this cluster arrive this week.
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06-17-2013, 06:47 PM
Post: #6
RE: Radeon HD 7990 Review
I was afraid heat would be a problem with those cards based on how the fans looked. I will be interested to know the results of putting it in a server case with better fans.
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06-17-2013, 11:20 PM
Post: #7
RE: Radeon HD 7990 Review
I had no chance to see it live in action, but seems it's design is just the same as GV-R695OC-1GD. So when it in chasis it takes cold air from it's bottom and blows it onto chasis side (card top), because of that atx case just should be 'open side' one, to not to lock-in air inside it. Some case with mesh on its side where card blows it's air. Huge fans in case can make situation better but not perfect because vortex inside case can disturb normal airflow. Why do I think that these cards will go into Tyan case without their native fans.
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06-18-2013, 01:46 AM (This post was last modified: 06-20-2013 06:53 AM by epixoip.)
Post: #8
RE: Radeon HD 7990 Review
yeah, the cooler is very similar in design to the GV-R695OC-1GD. however, the reference 7990 cooler is much more stout, and has a lot more copper on it.

they are going into a Tyan case; however, because the cards have longitudinal heatsinks instead of latitudinal heatsinks, we will not be able to run them without fans. which is very disappointing.
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06-18-2013, 08:24 AM
Post: #9
RE: Radeon HD 7990 Review
Ah, really, forgot how heatsink is placed on cards like this. Then on Tyan will be a bit problematic I think.
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06-18-2013, 10:41 AM
Post: #10
RE: Radeon HD 7990 Review
it would be problematic to try to passively cool it, yes. but i think it has sufficient airflow to prevent overheating with active cooling.
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