AMD have a long and storied history with dual-GPU graphics cards. Possibly the most well-known and well respected has been the Radeon HD5970, whilst the HD4870X2 was a genuine game-changer, but even more recently the HD6990 and HD7990 both created waves for performance. No matter the GPU used the formula is the same - two high performance GPUs on one PCB linked using CrossFire, essentially allowing them to work in tandem on tasks from gaming to compute.
Since the release of the Radeon R9 290X the question has been however if the Hawaii GPU can be tamed enough to cram in to one PCB. Notoriously hot and power hungry, both cooling and power infrastructure would have to be designed to cope with demands on the limits of the technology. Project Hydra was therefore conceived, tasked with leashing Hawaii and getting it into one card, without compromising on power. Today it appears that AMD have accomplished just that, as the Radeon R9 2905X2 takes its place as the flagship product in AMDs graphics lineup.
Technical Details
Each Radeon R9 295X2 is based around two full fat Hawaii GPU Cores each with all 2816 shaders activated. Rather than slimming down the cores in either clock speeds or shader cores to facilitate a lower power draw, AMD have instead pushed clock speeds to top even those of the R9 290X, with a speed up to 1018MHz. Like the rest of the R9 290-series it also utilises a dynamic clocking system as the two other Hawaii-cased cards, keeping the GPUs within a power envelope for a given fan and power profile achieved in PowerTune.
At 500W, the R9 295X2 has the highest typical power draw of any card yet released in retail channels. This is perhaps unsurprising given how much of a powerhouse a single full-fat Hawaii GPU turned out to be, but it's interesting that AMD haven't wanted to compromise in the means traditional to dual-GPU reference efforts. No doubt this is with an eye to the competition, who are soon to release the dual-GPU GTX TITAN-Z (which will cost approximately twice the price of the 295X2) and may yet also release a dual-GPU variant of the GTX 780/780Ti. AMD want there to be no wriggle-room - this should be the best card they will release this generation.
Unfortunately many PSUs will be unable to handle supplying 500W of power via two 8-pin PCI-E connectors. AMD are recommending fairly definitively that each 12V lane on a multi-lane supply be capable of supplying at least 28A (i.e. 28A per 8-pin connector) and the PSU 50A total just to the GFX (never mind the additional requirements of a CPU). A strong single-rail design will need to supply the whole of the requirements (50A + other system needs) on a single rail. This information will be found on your PSU info table, but as usual we would reiterate that in addition to the raw specs it needs to be a quality supply that can supply clean power and protect your components in the event of a problem.
AMD will be releasing a list of approved PSUs soon after the NDA drops which can be found here so kudos to them.
The memory infrastructure is similarly robust, featuring 8GB (4GB per GPU) GDDR5 RAM clocked at 5000MHz with a 512-bit wide bus; this will be crucial to realising the dream of 4K gaming with a single card/dual-GPU configuration. Two BIOS's are also featured, but this time there is no split between 'Quiet' and 'Uber' modes - instead just a stock and a backup. For those who appreciate a little tinkering that's certainly a boon, and is great just for general peace-of-mind.
Finally, the card is compatible with AMD's Mantle and TrueAudio Technologies, which it inherits from its R9 290 DNA. Multi-GPU support for Mantle is still in its infancy but should be maturing as we approach the second half od this year, but this titbit it also strongly implies that the R9 295X2 will be DirectX 12 compatible upon the release of Microsoft's new development environment.
All this strongly indicates that the Radeon R9 295X2 is one of the most technologically advanced and capable cards yet constructed, and bodes well for its future so long as the consumers can both get their hands on it and live with it.
Cooling Solution
AMD took a lot of flack for the R9 290X's reference cooling solution, which is we're honest was only just adequate for its temperature dissipation needs. Traditionally dual-GPU solutions are even more of a challenge, which first made use of a blower cooler and then graduated to ever more elaborate setups as requirements became yet more constraining. As such AMD obviously felt that something novel was required, and so they enlisted the aid of Asetek to create a new and effective system specifically for the dual-GPU R9 295X2. What they came up with was certainly that.
The R9 295X2 is the first card to have a reference cooling solution utilising a closed loop liquid cooling system for the majority of its heat dissipation. The system is custom to this card, featuring one microchannel heatsink per GPU and an extended loop connected to a 38mm-thick 120mm heat exchanger (radiator). The choice allows maximum compatibility within a range of chassis, and is a proven very low maintenance solution similar to those run to cool CPUs of highly overclocked systems for years. A tubing length of 380mm should be just long enough to enable a range of mounting positions within most mid-to-full tower chassis designs.
Providing additional cooling to other components is a single fan in the centre of the card. As it's not required to cool the monstrous GPUs it can run at a lower RPM, simply providing slightly more than incidental air flow to cool important secondary components such as memory modules and VRMs. Air flow is directed by an anodised aluminium shroud, whilst a metal backplate will also help to spead the heat of toasty backside memory modules. Although the heat is sped away from the cores to the radiator, you'll still want your chassis fans to supply plenty of cool fresh air into the case.
Noise generation will very much depend on the conditions internal to your chassis, but AMD are projecting that the card will be approximately 3dB quieter than the R9 290X Quiet Mode at load. That's a considerable improvement to past dual-GPU configurations. Furthermore, for your aesthetic needs the shroud has a single illuminated red Radeon logo and fan, although unfortunately neither can be controlled directly via hardware.
Expected Performance
The R9 295X2 is effectively two R9 290X GPUs running in CrossFire on one PCB, and has performance roughly congruent with that. Support for dual-GPU configurations has in the past been spotty, but where two GPUs can be leveraged the scaling can be extremely impressive - if not quite fully double that of a single GPU. AMDs own internal benchmarks place scaling between 175 and 190%, or to put it another way the twin GPUs will crunch pixels almost twice as fast as one of those GPUs. Such was not always the case, and it's only following the extensive work of hardware and driver engineers that these returns can be realised.
Unsurprisingly however AMD are touting the R9 295X2 as being the card for 4K gaming thanks to its copious 8GB RAM, 512-bit wide memory bus per GPU and two Hawaii XT GPUs with the taps turned up to the max. Internal benchmarking from AMD places it beating two SLI'd NVIDIA GTX TITAN Blacks (when both are at stock configurations), but just as crucially indicates frame rates at or considerably above the key 30fps figure, finally knocking on the door of the 45fps needed for a truly good gaming experience.
Ultra HD/4K gaming monitors are just starting to infiltrate the market at affordable (from £500) price points, and so it's no wonder AMD are targeting this resolution on their flagship GPU. As on would be forced to expect enjoyable (as opposed to merely playable) frame rates will be contigent on system settings, but the R9 2905X2 looks to be the first single-card solution to really broach 4K as a playable resolution for AAA-titles.
Price and Availability
The R9 2905X2 is a premium product, with a price to match. At the time this article went to press AMD are quoting a price of €1089 + V.A.T. / $1499, which reflects both the high current demand for the Hawaii XT GPU and the 8GB GDDR5 RAM built in to ever board. It's expected to be available at etailers from April 21st.
Our verdict on the Radeon R9 295X2 will wait until it's been through our own tests, but as always the engineering achievements required to cram two high performance GPUs seamlessly onto own PCB leave us near breathless. That AMD have also taken obvious care with the cooling solution - addressing concerns not only arising from the original reference Hawaii cards but also previous dual-GPU design - and come up with a novel idea that should be both effective and quiet is also worthy of special praise.
Dual-GPU cards are always a luxury, even in a world now populated with multiple >$500 GPUs. Whether or not to buy one is dependant on your own financial circumstances as well as the system you have built or intend to build. Not all chassis will be appropriate, and greater care than usual will need to be taken with your average component choice. However all in all the R9 295X2 looks set to find a home with those who want no compromise 4K gaming, but in as compact a design as possible.
For more official information visit http://www.amd.com/295X2.
