AMD's engineering pedigree for dual-GPU solutions is well established; a tradition which has its roots in ATi’s dual-GPU Radeon HD cards since the R600 generation – otherwise known as the 3000-series. Highly notable in that timeline have been the 4870 X2 and 5970, both phenomenal feats of engineering which represented class-leading performance upon release and for some time thereafter. An official dual-GPU GCN card based on the 7000-series Tahiti XT GPU therefore seemed inevitable.
In August AMD partner Powercolor released the dual-Tahiti - but unofficial - Devil13 HD7970X2, with manufacturers such as ASUS following suit early this year. One in particular, the ASUS ROG ARES II, has gone on to win performance accolades as a boutique card well into the £1100+ range. Still, at that time everyone anticipated an official AMD HD7990 which never materialised, perhaps as much down to a focus on the value presented by the HD7970 and not wanting to take too much of the limelight away from their partners. We should also note in that time AMD have made great strides in their driver development program, which may also have delayed any new design releases that relied on notoriously temperamental dual-GPU communication.
Which brings us to today, where as far a reference designs go AMD have in play the HD7970 GHz Edition with Boost, but not much more to face down the threat of NVIDIA’s GTX Titan. As we know the GPU on the GHz Edition card is the revised Tahiti XT2, an update based on a maturing 28nm process yielding higher frequency capabilities and enabling dynamic overclocking; great as this GPU is, it’s no threat to the 800-pound gorilla in the room. AMD therefore have chosen to release what they hope will be their ace in the hole – the HD7990 ‘Malta’.
Malta incorporates two Tahiti XT GPUs with reference clock speeds pegged at 950MHz boosting to 1GHz – a little down from the awe-inspiring 1.1GHz of the liquid cooled custom ROG ARES II – and 6GB GDDR5 RAM. All told that’s 4096 stream processors, 64 ROPs and memory operating at 6Gbps through an 384bit memory bus per core; impressive headline figures I'm sure you'll agree. AMD believe that’s enough to comprehensively best the NVIDIA GTX 690 on all relevant gaming benchmarks, and presupposing the GTX 690 is faster than the GTX Titan – a reasonable suggestion generally borne out by our own benchmarks – this would peg the AMD HD7990 as the fastest single card on the market of all the reference designs.
Unfortunately specs alone aren't enough to win the day, a factor which AMD are all too acutely aware of. Their most recent dual-GPU solution, the HD6990, came in for some well-deserved flack on release due to a particularly noisy reference cooler which struggled to keep a dual-GPU solution under control. As a result AMD have gone back to basics, seeking a solution which above all kept the GPUs cool within a low noise envelope. They specifically targeted the GTX Titan, aiming quite reasonably to keep noise below the level of NVIDIA’s reference solution and make the HD7990 a card you can live with. The consequent cooler design utilises three axial fans and a dedicated heatsink with 4 heatpipes for each core, resembling a high-quality aftermarket solution rather than typical reference design. The PCB is also backed by a heatspreader, cooling the components and improving the overall card aesthetics. AMD state that whilst under Furmark the design keeps the noise levels below that of the GTX Titan and even a quiet room environment (~40dB); if so, this is an achievement to say the least.
Power-wise, the HD7990 isn’t a lightweight. Although no official figures have been provided the card nonetheless requires two 8-pin PCE-E power connectors, although we imagine that the card will not come close to hitting the max power draw for this configuration. Despite the performance nature of the product AMD have still included ZeroCore technology, which places the 2nd GPU in a very low power sleep mode if not in use (i.e. when not gaming). In theory this should mean that even though at its heart it's a thoroughbred performance card it should remain fairly power efficient, especially for users who do more than game on their systems.
However, AMD are not content and are looking forward to future conditions which will affect the gaming market. On the horizon are 4K display resolutions – still many years out for most consumers but certainly on the radar for the high-end enthusiast. In testing both Crysis 3 and Tomb Raider (2013) were playable at 3840 x 2160 with maximum quality settings (inc. TressFX for Tomb Raider), internal testing putting the performance of Crysis 3 under this scenario at 35-40fps. Without doubt this is impressive, which AMD claim is only possible with the HD7990 as a one-card solution.
Similarly triple-monitor displays featuring 1080p resolutions are becoming more commonplace and requires targeting. Although capable of five or more displays with appropriate equipment, the HD7990’s benchmarking will most often be against the GTX 690 in 3 x 1080p configurations and AMD believe that they have their competition licked here too.
Extremely high resolution performance is augmented by the major innovation on the HD7990: the inclusion of a new PLX chip capable of 48 lanes of PCE-E 3.0 for an interGPU bandwidth of 96GB/s, more than another other consumer GPU to date. Just how much of an impact it currently has will be open to debate, but it would not be too much of a surprise for this platform to be a proving-ground of sorts for technology applicable to later generations. AMD did stress that it's not a solution to the micro-stutter issue seen on some dual-GPU solutions, which is an artefact of a problem unrelated to GPU interconnect bandwidth and still being worked on by internal teams.
Finally, we get to the crux of the matter: the price. Perhaps unsurprisingly the card is set to retail at £719 + V.A.T., or £862 inc. V.A.T., which is considerably more than you would expect to pay for two HD7970 GHz Editions from a high value partner. For your money you will have bought a card with significantly fewer case/motherboard/PSU compatibility issues and slightly better driver support than is typical with two-card CrossFireX solutions. Furthermore a bundle of seven games including BioShock Infinite and Far Cry: Blood Dragon are included in the mix as part of the Never Settle program, providing additional value which shouldn’t be discounted.
When the HD7990 becomes available at etailers in the next couple of weeks it will be, like all previous dual-GPU cards, a niche solution. Those with the best part of £1000 to spend will have to weigh up the pros and cons of either a faster dual-GPU card, or slower GPU that sidesteps any CrossFireX/SLi problems. We shall have to wait on Rich’s head-to-head test of the HD7990 vs the GTX 690 to see which comes out ahead and take the single-card crown. Till then, we ponder if NVIDIA have something up their sleeves and keep the competition fierce.
For more information on this and other graphics solutions from AMD visit AMD.com