AMD HD6990 Review Page: 1

AMD HD6990 Review

Introduction

It feels like it's been a long time coming, the dual-GPU HD6990.

The reality is that it hasn't, rather our initial experiences with the current range of HD6xxx graphics cards from AMD were disappointing enough that it felt like we'd been waiting forever.

So here it is in all its glory. Similarly to most dual-GPU single-board solutions we haven't got two of the top-end R6970 chips here, but rather a combination of two chips that would be a theoretical HD6960.

Is this the card with which AMD reclaim the crown?

Technical Specifications

From a technical standpoint the numbers are, as we'd expect, mind blowing. Everything about this card shows how hard AMD have been working to cram the 6990 full of their finest hardware to ensure it has the best chance possible to be the ultimate single-card solution.

AMD HD6990 Review



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AMD HD6990 Review

Up Close

The HD6990 follows the current AMD theme of a black shroud with three red stripes upon it. It's odd that after destroying any brand identification with the renumbering fiasco they'd go to such lengths to show the cards similarities.

Instead of twin DVI and a HDMI or DisplayPort, the HD6990 supports Eyefinity via DisplayPort and adaptors. So you have a single DVI for most of us, and four mini-DP outputs should you desire surround gaming.

AMD HD6990 Review     AMD HD6990 Review  

Nothing warms the heart quite like the sight of two GPUs on a single board. You can feel the power flowing through before it isn't fired up.

Cooling taken care of with the same cooler we saw on the HD6970, just with an extra GPU block and the fan relocated to the centre. It doesn't fill us with confidence we have to admit. Heat begets heat.

AMD HD6990 Review     AMD HD6990 Review  

Once the main body of the cooler is removed we can see the board in all it's glory. A few of the features we'll get to on the next page, but for now we have the two GPUs bookending the power phases and encircled themselves by the GDDR5.

Apparently the HD6990 has "phase-change thermal interface material". Sure looks like regular paste to us.

AMD HD6990 PCB     AMD HD6990 Review  

Keeping two GPUs happy means two 8pin PCIe power inputs, but that's obviously less than are needed for two, even medium, cards. Makes cable routing far easier.

AMD HD6990 Review     AMD HD6990 Review



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AMD HD6990 Review

Under the Skin

Naturally when designing such a behemoth a lot of consideration has to be made as to the best way to ensure you can supply two GPUs with the power that they need, whilst still keeping the temperatures low enough to not make the sides of you case start liquefying.

Whilst you could have 20 GPUs on a board if yo had the time and inclination, keeping them powered would be something else altogether. As extreme an example that might be, it is an identical problem with two. If a single GPU requires 6+8 or even 8+8 PCIe power connectors, then how do you keep two rocking? With immense voltage regulators of course. Centrally mounted to ensure the smallest path possible so that neither GPU lags behind the other.

AMD HD6990 Review  

If the GTX480 taught us anything it's that huge power draw and performance is pointless without sufficient cooling.

To that end AMD have supplied the HD6990 with a centrally mounted fan blowing air across two vapour chambers, one for each GPU. The most intriguing aspect is the use of a phase change thermal compound. That sounds great and very technical, but water boiling into steam, or ice melting, are both phase changes. It doesn't mean they are desirable. Equally if all that happens when the TIM gets hot is that it drips out the card, it wont be very helpful.

AMD HD6990 Review  

Finally the nice surprise is that there are two BIOS on board the HD6990. Flicking between the two is like taking a very angry bear, then poking it with a stick. Should be a blast, and at worst allows the user a level of control over the power-draw of the HD6990.

AMD HD6990 Review



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AMD HD6990 Review

Test Setup

AMD Radeon HD6990
Intel Core i7-950 @ 4GHz
ASUS Rampage III Extreme
Muskin Joule 1200w
6GB Mushkin Redline
Noctua NH-D14
Windows 7 Ultimate x64

Overclocking

We've got two overclocking results for you today. The first is the current overclock maximum which gains the HD6990 another 45MHz. You can run this all day if you desired. The Memory overclock is particularly impressive given the normally poor GDDR5 overclocking performance of GPU memory.

AMD HD6990 Review 

Our second overclock is more of a "future potential" one as the chip can easily do it, but the cooling solution is utterly incapable of dispersing the heat produced. So once the AMD Partners bring out their tailored versions we should start to see overclocks heading towards 1GHz on the core.

 AMD HD6990 Review  

Temperatures

Speaking of heat, this cooler is just not up to the task at all. It's woeful. But more of that in the conclusion, for now, 89°C maximum after an overclocked 3D Mark Vantage run should be enough to give you an idea.

AMD HD6990 Review



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AMD HD6990 Review

3D Mark Vantage

Always a good test of raw horsepower with modern cards, the HD6990 puts up a fabulous showing straight out the gate. It's nearly identical to two separate HD6970s in Crossfire. Price wise it's perfect too being right between a single and SLI GTX580s. The SLI GTX580 P score is off the graph because that's not why we're here today. The HD6990s X score of nearly 21000 is 4000 points better than the ASUS Ares and the Sapphire HD5970 TOXIC. Impressed yet?

 

3D Mark 11

If the HD6990 looks good in Vantage, in the modern, shader heavy, DX11-based 3D Mark 11 it's even more impressive. Whilst it obviously can't keep up with the GTX580 SLI, it's neither designed nor priced to either.



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AMD HD6990 Review

Unigine

One of the biggest strengths of the HD6 series from AMD is its ability to Tessellate with the best of them and it's given us some of the highest scores we've seen in this benchmark. Indeed you can see from the graph that the HD6970 Crossfire setup gives nearly 150 FPS average. Unbelievable heights for such a testing benchmark. Sadly the same can't be said for the HD6990 as it's just nowhere near as good as we hoped. Perhaps the early drivers are to blame here.

 

With the image quality set to maximum we have a similar result. The new Anti-Aliasing algorithms are doing their job though as the drop-off from using 8x AA is only 25% compared to the 33% of the HD6970 CF setup.



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AMD HD6990 Review

Alien vs Predator

Anyone still wondering what the fastest single card solution is?

The HD6990 almost sneers at AvP maxed-out giving frame-rates well in the triple digits and twice that of the GTX580.

 

Crysis Warhead

It would be pointless to put Crysis Warhead on our normal 0xAA Gamer settings here. With the BIOS in the overclock mode the HD6990 pumps out a frankly ridiculous 78FPS. With Crysis 2 a heartbeat away it's a fitting send-off for the Ice-Locked Island. Crysis Warhead how it's meant to be played. Took long enough to get there.



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AMD HD6990 Review

Far Cry 2

Ubisofts take on the open-plan FPS still looks as amazing today as it did then and few things are more enjoyable than an exploding barrel to the wedding tackle of your enemy. It's here where you can see the limits that two GPUs on a single board have over two separate cards. The HD6970 CF which has kept pace throughout testing so far pulls out a handy lead and the GTX580SLI really asserts its dominance.

 

Metro 2033

Now here is a game built for this card. No amount of insane hardware will push it along at remotely the levels that two, even mild, GPUs will in comparison. So it proves with the HD6990 once again neck and neck with its brethren and a mile ahead of the single GTX580.



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AMD HD6990 Review

Conclusion

Semantics are always important. Precise wording can be the difference between the truth and a lie, when to the average person you're saying the same thing.

For example, if I now say the HD6990 is the fastest single GPU on the planet, that's not strictly true. Two GPUs of course. But then it's not the single fastest twin GPU solution either. That still understandably belongs to the crazy-fast GTX580 in SLI.

What this is is the fastest SINGLE CARD graphics solution available. And oh boy is it.

Given the slightly average performance of the HD6870 and HD6970 we all knew that AMDs eggs were most definitely in the HD6990 basket, but would they drop them on the way to market. Thankfully for all of us they've delivered something that is bad to the bone. No matter what you throw at the HD6990 it just shrugs its shoulders and ploughs ahead. 

It's hugely faster than its generational predecessors. The previous ATI Kings were the two bespoke offerings from Asus and Sapphire, the Ares and Toxic respectively. This is in another league entirely and for about 60% of the price of either of those.

Sadly for every Dr Jeckyll there is a Mr Hyde, and the Mr Hyde for the HD6990 is the cooling solution. Even calling it a cooling solution seems to be overstating things. It's a fan that spins and some metal.

We, in descending order, like our heatsinks to be three things.

Firstly they must cool. We can forgive almost anything if the cooling potential is good enough. Nobody considered LN2 to be the height of design genius, but nobody cares because it's epic.
Secondly we like it to be quiet. When we tested the HD6970 we said that the fan seemed depressingly reluctant to actually spin up and shift the hot air, but at least when it did it was fairly quiet.
Finally, if both the above are taken care of, we like it to be aesthetically pleasing.

The MSI Twin Frozr II springs to mind as something which does all three, being amazing at cooling, quiet as a hoarse mouse and seriously gorgeous.

This.

Isn't.

We experienced more than one thermal shutdown during the testing, and the card didn't even start to be cool until the fan was at 60% or more, by which point our ears were bleeding with 40% further to go.

Pricing starts at about £520 for a reference one, which is about identical to a couple of HD6970s and plenty cheaper than two GTX580s.

So all in all the underlying card is fanfreakingtastic, but let down horribly by the reference cooler. We can't wait to see what the partners bring to the table because with a half-decent cooler this really will be tough to resist.

    

Thanks to AMD for providing the HD6990 for review. Discuss it in our forums.