Authour: James Prior
Editor: Charles Oliver
Date: March 8th, 2011
AMD Radeon HD 6990
'Crazy like a Sheen' is a good place to start. Like the other members of the 6900 series, the HD 6990 features a dual BIOS; unlike its single GPU brethren, the two modes offer different performance levels. In stock shipping form, the Radeon HD 6990 runs a 830MHz GPU core speeds on its cherry picked low voltage, low leakage Cayman XT cores with the full 1536 VLIW-4 cores of the 6970. Memory clocks are down, to 1250MHz - a 'mere' 5Gbps speed from the 2GB of GDDR5 per GPU. AMD Powertune technology limits maximum board power to 375W, the maximum electrical specification of the power available from the 75W PCI-Express slot and two 150W 8-pin power inputs. In practice, as with the rest of the 6900s, power draw is lower but still not under 300W as PCI-SIG requires for the official add-in board rules. Well, they're more like guidelines, anyway ... AMD hasn't yet provided a list of OEMs or system builders featuring the HD 6990 yet, but one will most likely include only the custom boutique vendors rather than the traditional big names like Dell or HP gaming divisions.
The second BIOS mode increases GPU core voltage, PowerTune capacity limit and core clock speeds. We now get 880MHz GPUs and a 450W PowerTune limit offering all the performance the GPUs can muster for those in possession of hirsute and sizeable gonads. Now you can see where the rumors of two cards being launched came from. The single board power draw capabilities seem ridiculous until you recall that two HD 6970s, or NVIDIA GTX 570s for that matter, are going to draw more power - and enthusiasts don't blink twice about specifying a suitable case and PSU to cool and power those ultra-enthusiast solutions.
Physically the card is the same form factor as the ATI Radeon HD 5970, arguably the previous World's fastest graphics card. AMD has held the high-end crown now since the launch of the ATI Radeon HD 5870, if not the fastest single GPU card, using their sweet-spot strategy to make a GPU that scales well to Crossfire-on-a-stick. AMD PowerTune technology allows them to ship a card that safely runs all the way up to the electrical specifications of the power inputs, although typical gaming power is going to be well under at around 350W - although this is not an inconsiderable amount.
New Cooling Design
A new cooling design debuts with Antilles, with a centrally mounted large diameter axial fan. This exhausts air out of the rear of the case as well as the rear of the card, back into the case. This cools the centrally mounted Volterra digital programmable regulators, now more efficient and higher power, as well as feeding air directly to each GPU and memory set instead of feeding the heat from one to the other. Memory is located on both front and back of the board, making the rear backplate on the card functional as a heatspreader instead of just for looks and component protection. The ASICs are cooled individually using large vapor chamber heatsinks, mounting using special phase-change thermal paste that hardens after heating to provide the best thermal conduction possible. Overall, there is 20% more airflow compared with the HD 5970.
The rear outputs of the card are dominated by the four mini-DisplayPort outputs, and the whole slot exhaust grille. A dual-link DVI output is also featured, offering out of the box Eyefinity-5 capabilities - a configuration added recently in the Catalyst 10.2 drivers. AMD also includes three adapters, including one active mini-DP to DVI output - three DVI Eyefinity is possible with no extra purchase. A mini-DP to HDMI 1.4a adapter is also included.
In performance terms AMD claims (for OC mode) on average a 69% increase over the $499 NVIDIA GeForce GTX 580. While we haven't fully evaluated this claim yet, we can tell you that the specifications promise Radeon HD 6970 Crossfire on a stick and that's what you get. This card is made for ultra-enthusiasts, be they image quality or performance enthusiast types. Gaming at 1920x1080 with this card will provide you with the performance to run all the AMD driver options you desire, from SuperSampled AA (Dx9) to MLAA and EQAA (All Dx versions) in many, many titles. It'll do this in a small form factor than Crossfire 6970's and offer more overclocking headroom, as for the HD 6990 the CCC overdrive limits are sky high.
At $699 this is not a value proposition, and AMD hasn't treated it as such - this is all the way, flat out as fast as they can go for a graphics card; very refreshing to see, and doesn't bode well for NVIDIA's rumored upcoming GeForce GTX 590. Gaming at 1920x1080 with this card will provide you with the performance to run all the AMD driver options you desire, from SuperSampled AA (Dx9) to MLAA and EQAA (All DX versions) in many, many titles. It'll do this in a smaller form factor than Crossfire 6970s and offer more overclocking headroom, as for the HD 6990 the CCC overdrive limits are sky high. Our testing so far shows that AMD's estimates of actual power draw are very accurate, and it runs quite cool for such a powerful card, using less power than the equivalent discrete two cards.
And performance? While we're disappointed in the use of slower 5Gbps memory chips rather than the 6Gbps ones (clocked at 5.5) from the 6970, we can't say that we've seen it meaningfully impact performance, but it may limit ultimate overclocking speeds. This seems to be the only design decision made as a concession to board power and heat, other than the 830MHz core clocks: drop the memory clock and specify lower power chips to give back TDP for the GPU cores. Alternatively it is a cost saving measure - sixteen of the fastest possible GDDR5 chips push an already expensive card higher. In value terms, only the 6950 seems to challenge it - if you get two that unlock the extra SIMD units, and Crossfire them ... and overclock them.
AMD VISION Black
AMD claims immediate availability but it may be a few days until all partners get their products into the retail channel; if you're looking for one, grab it when you can. For the stout of heart two can be combined for 4-GPU CrossfireX but you'll need to be sure your system can handle the load - a single card, in OC BIOS mode, will draw around 38A from the 12V all by itself; two could be monstrous. But then, if you're laying down over $1400USD for two of the World's Fastest Graphics Cards, another $300 for a quality 1KW+ Power supply shouldn't be an issue - or you're doing it wrong. We'll bring you our full performance and feature testing results as soon as we can.
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