PowerColor AX6990 4GBD5-M4D Video Card E-mail
Reviews - Featured Reviews: Video Cards
Written by Bruce Normann   
Sunday, 20 March 2011
Table of Contents: Page Index
PowerColor AX6990 4GBD5-M4D Video Card
Closer Look: PowerColor Radeon HD 6990
PowerColor Radeon HD 6990 Detailed Features
Features and Specifications
Video Card Testing Methodology
DX10: 3DMark Vantage
DX10: Just Cause 2
DX9 SSAO: Mafia II
DX11: Aliens vs. Predator
DX11: Battlefield: Bad Company 2
DX11: DiRT-2 Demo
DX11: H.A.W.X. 2
DX11: Lost Planet 2
DX11: METRO 2033
DX11: Unigine Heaven 2.1
PowerColor HD 6990 Temperatures
AMD Radeon HD 6990 Final Thoughts
PowerColor Radeon HD 6990 Conclusion

Closer Look: PowerColor Radeon HD 6990

The PowerColor AX6950 4GBD5-M4D is based 100% on the AMD reference card, which is a completely new design. As of the moment there are no AIB partners that are game enough to design and produce their own version of this card. At best, I expect one or two may offer a different cooling solution, but the board design is probably going to remain the same for the foreseeable future. Let's start at the top.

The first thing you notice when you pick up this video card is that it's very long, and relatively thin, or at least not thicker than any other reference card. The second thing you notice is the weight and the fact that's it's both better balanced and distributed along its length. None of this should be a surprise if you think about it for a second, but no one stops to think when they're unboxing the most powerful graphics card in the world. Oops, did I let the cat out of the bag? Too late, I think AMD got there first.


The fan shroud is a completely sealed-off design; there are no extra relief vents anywhere to be seen. Both ends are relatively open and the airflow path is as uncluttered as they could make it. The straight through design of the fin assemblies and the lack of restrictions at both ends help out on the noise performance as well. NVIDIA did the same thing with their GTX 580, with the same general effect.

The single 80mm radial fan is placed right at the center of the card and pushes air out in two directions, along the length of the shroud. The two GPUs are spaced out a fair distance from the center and each has its own dedicated fin assembly sitting atop it. The component level on the PC board is cooled by full size cast aluminum heat spreaders on both the front of the card and the back. The one on the front catches the heat from all the Voltage Regulator Modules, as well as half the installed GDDR5 DRAM. The other half of the 4GB total is mounted on the back surface of the board and they are pretty much the only major heat producers located there.


The cooling fin assemblies do away with heatpipes completely, and use full-sized vapor chambers instead. They operate on the same principle as heat pipes: using specially selected refrigerant fluids that change phase at the operating temperature involved, and naturally occurring convective currents. As the gas rises, it is cooled by the aluminum fins and returns to its liquid state. This type of evaporative cooling is one of the most efficient heat transfer methods and is used in lots of high temperature applications such as nuclear power plants and inside the exhaust valves of high performance combustion engines. In that case, sodium is used as a very high temperature coolant inside the valve stem, transferring heat away from the valve face which is getting pummeled by a couple thousand explosions every minute the engine is running at normal highway speeds. The liquid inside these vapor chambers is more like the FreonTM that's inside your typical refrigerator or air conditioning system.


The back of the card is almost completely covered with a black anodized heat spreader, with cutouts for each GPU, and the tensioned skeleton backplate that holds the mounting screws for the heatsink/fin assembly. It's too bad no one has figured out a good way of removing heat from the back side of the board, right underneath the GPU. This section gets plenty hot, but there are over a hundred small capacitors and resistors in this area that you don't want to short out. Thermal tape to the rescue?


The thermal interface material (TIM) used by AMD on this card is a new "Phase Change" type of material that few people have had hands-on experience with. AMD warned all the media contacts that the performance of the card would be permanently degraded if it was disassembled, due to the unique properties of this TIM. Many thanks to W1zzard over at techPowerUp, who showed no fear and disassembled his card to report on this mystery TIM. Info from the US Patent Office (#6,620,515) calls this class of materials: "A phase change composition comprises: a matrix comprising an organofunctional silicone wax, and a thermally conductive filler. The composition can be used as a thermal interface material in electronic devices. The composition is formulated to have any desired phase change temperature." That's a pretty broad description, but the bottom line is that the usual grease-based carrier material has been replaced with a wax-like substance that thins out better at typical operating temperatures. This minimizes the impact of the carrier material and allows the filler material, which is many times better at conducting heat, to make better contact with the surfaces of both the heat source and sink.

I have never had the thermal performance of a video card degrade after I've taken it apart and reassembled it with a smaller amount of high quality TIM paste, but this time I think I've met my match. The thermal design of this card is so close to the edge of meltdown that I don't want to mess with it. Show me a full coverage waterblock that I can bolt on, and then I'll take it down to its bare essentials. For those braver than I, who end up succumbing to their curiosity and DIY spirit, please read the thorough discussion of best practices for applying TIM available here.


The layout on the front and back of the printed circuit board is very unusual, just as you would suspect, given the design brief. The current paths for power are made as short as possible by grouping the main voltage regulator module sections between the two GPUs, and by locating the highest current ones feeding the two GPUs along the top edge of the board, where they are closer to the power input connectors. As the highest of high-end graphics cards, the PowerColor Radeon HD 6990 is a necessarily complex and tightly constrained product. The designers at AMD had very little design flexibility when faced with the overwhelming amounts of power and heat that are involved here.


One final thing we need to look at is the installation of this oversized card in a modern gaming case. Owners of the previous model HD 5970 are well aware that the length of the card could be a problem when choosing a PC chassis. I measured 305mm from front to rear on my sample. Thankfully, this number doesn't need to be fudged with some imprecise allowance for PCI-E power connectors, as the two 8-pin connectors are located along the top edge. In my test bed PC case, which is a CM Storm Sniper, I had 35mm of extra room left over between the far end of the card and the drive cage framework. I had no problems getting the card in or out with this much clearance, especially since I didn't have to worry about accessing any power connectors on the end of the card. And yes, I know my cable management is a mess, and yes that is painter's tape on my CPU cooler. You wouldn't believe the amount of air that comes barging out from the gap between the fan housing and the fin assembly without it.

In the next section, let's take a more detailed look at some of the new components on this non-reference board. I didn't do a full tear-down, but AMD graciously provided some detailed images that will allow us to see everything of importance.



# RE: PowerColor AX6990 4GBD5-M4D Video CardRobert17 2011-03-20 15:16
Well done Bruce. After all the effort, sacrifice, and no telling how many years of enthusiasm/experience you bring to the fray, I feel compelled to offer a sacrifice of my own. Since the card is out of warranty, I volunteer to take it off your hands for long term testing, say a couple of years, and deal with any and all warranty issues in your stead. I know, I know, my altruism knows no bounds.

(wink, wink, nudge, nudge)

Good job.
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# Counter OfferBruceBruce 2011-03-20 16:19
Thanks for the props, Robert. As for your boundless altruism, I'll go you one better. You put gas in my wife's car for the time that you have the card, and it's a deal. [%^)
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# RE: Counter OfferRobert17 2011-03-20 16:22
Does she actually drive it?
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# Just got mineCom-Tek Chris 2011-03-22 06:43
I know this was written for the PowerColor card but I just received my HIS yesterday and installed it last night. I guess my bottle neck is my resolution and my monitor. I have a 28" 60Hz, 1920x1200 Hanns-G monitor with 3ms response. I just don't see the gain from this series and going back to my 2x 465 GTX Nvidias or my 2x 580 GTX's in SLI. For the ATI fans I also have 2x 5850's in X-Fire and they also run like beasts. Its kinda like having a Race Car that does 205+ MPH but because you live in a heavy school zone there are always police which limits your choice to either follow the law or get arrested (Kind of a bad analogy but I'm sure you get my drift).

So now I have spent $720 on this card, damn I need a new hobby, I've now spent over $2,500 on video cards in the last 6 months.
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# RE: Just got mineOlin Coles 2011-03-22 07:17
I'm curious what kind of games you're playing, because that could be an indication of your bottleneck. Anything will play Battlefield or Starcraft at high frame rates, but the same cannot be said for titles such as Metro 2033.
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# RE RE: Just got mineCom-Tek Chris 2011-03-22 07:33
I'm playing Battlefield Bad Company 2 and a few other FPS games. I figured that was my problem. And BFBC2 is more CPU intensive, I playing Battlefield on my AM3 1090T 6 Core which is more than enough for that game. I need to start HA (Hardware Anonymous) for geeks, but I'm afraid it would be a blood bath of which brand name was better, lol.
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# A thoughtCom-Tek Chris 2011-03-22 06:59
How come we are pitting this against the Nvidia 400 series and not a set of 560ti's in SLI or a a single 580 GTX? I notice that the scores are up against a set of 460 GTX's in SLI and a couple of 6xxx series in cross-fire mode but none of the big cards from Nvidia in SLI. Was this because of a price to power thresh hold? Or because of availability in cards? I know my 2 580 GTX's his the $1,100 mark when I purchased both so maybe it is unfair to compare it to a single card that is $400 less, but still it would be nice to have the scores posted for comparison for both sides of the fan base. Hands down though, I love this 6990, its fast, sweet, and feels like there is a lot of technology in it. Even Nvidia Fan Boys would be impressed with the sheer speed of this card.
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# RE: A thoughtOlin Coles 2011-03-22 07:18
If we had two of everything, we'd put them in SLI or CrossFire. Since one card arrives as another is ready to launch, we're restricted by deadlines and must move to the next project.
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# RE RE: A thoughtCom-Tek Chris 2011-03-22 07:34
Do you have to send back the cards your given? If not what do you do with them? Or do I dare ask, lol.
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# RE: RE RE: A thoughtOlin Coles 2011-03-22 07:37
Only a few products get returned, but it's a matter of finding time to review more than one product of the same series before the next arrives. These reviews take more time than you could imagine (I invite you to try sometime), and after one article in published a manufacturer usually has something new in our hands.
All of my video cards sit in a giant cardboard box, and get sold about 16 months after they've launched and gone EOL.
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# RE: RE RE: RE: A thoughtCom-Tek Chris 2011-03-22 08:43
I have done Bench Marking in the past with all new hardware, always trying to squeeze that extra 100 points out, lol, I don't do much anymore just because of the time it takes. I am a business owner and there are days where I start at 6am and get home at 10pm only to find that I have a 1/2 dozen build outs that are to be done by the next am, so I pull a 24hr shift that turns into a good 36hr shift, lol, did I mention I have a wife and 5 kids?...................so the drama continues in the life of "Im a computer engineer/network security consultant/Father/Guy who likes to game/Guy who races cars in the SCCA in the season which is here now/Guy who builds computers and provides support for local residents and business's and also donates computers to new local schools that burnt down 2 years, lol, yes I love life and all it offers..........did I mention I love Chinese food and hot pockets?
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# RE: RE: RE RE: RE: A thoughtOlin Coles 2011-03-22 08:48
Replace kids with friends, keep computer engineer/network security consultant/SCCA racer, and add target shooting enthusiast. Also replace Chinese food with Thai, and hot pockets for Wheat Thins, and we're on the same page.
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# Thanks BruceCom-Tek Chris 2011-03-22 07:15
Thanks Bruce for the in-depth article, it was very informative and I'm sure will encourage decisions on owning this card. Keep up the good work.
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# You're WelcomeBruceBruce 2011-03-22 20:34
Olin's spot on about product availability v. time to do the review. As Einstein said, "The reason time exists is so that everything doesn't all happen at once." My corollary to that is, "Space exists so that everything doesn't all happen at the same place."

So, check out Olin's HD 6990 reviews for comparisons to the GTX 570 and 580 cards. I was surprised that the 580 SLI didn't wipe the mat with the competitors. It was faster, but not in another league, you know....

I'm very curious to see how well NVIDIA manages the balance between electrical power, heat and processing power with their rumored dual-GPU card. At this stage of the game (40nm GPUs), there's only so much juice that you can pump through a single card and the winner is the one that's more efficient per watt. We'll have to wait another week or so, to see.

FWIW, I prefer Triscuits....LOL
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# RE: You're WelcomeOlin Coles 2011-03-22 20:37
Ah, Triscuits and wine cheese. One of my nostalgic favorites!

PS: Check back here at 6AM PST on 03/24 for "The Next Big Thing".
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# RE: RE: RE RE RE: RE: A thoughtCom-Tek Chris 2011-03-22 09:07
My wife pushes the wheat thins/Crackling Oat Bran Cereal.....a lot! And I just tried Thai recently, the curry wasn't to bad. My goal is to lose 30 pounds this year. I just got over the Flu and I have kept 12 pounds of that off, lol, its going to be a good year. Now if I can just get my hands a new AM3+ 8 Core, another 6990 for X-Crossfire Mode, now that would finish the year off with a POW!
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# PC Case SizeVaughn Janes 2011-03-22 16:49
What PC Case do you have in that picture, I hope its not really expensive. If it is do you think you could link a cheaper Pc case?
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# CM Storm SniperBruceBruce 2011-03-22 17:30
It's a CM Storm Sniper, which I reviewed here: benchmarkreviews.com/index.php?option=com_content&task=view&id=398&Itemid=61

It's not cheap, unfortunately, unless you find a deal. The good news is that there have been a ton of inexpensive gaming chassis reviewd on this this site recently, and I'd bet at least half of them would be able to handle this card, at 305 mm long.
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# Forgot to make it a replyVaughn Janes 2011-03-22 17:39
Ok Coolio, its way cheaper than the one I found (##shopbot.ca/pp-corsair-obsidian-800d-corsair-price-208226.html) Thanks.
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