You need a bit of power for this
Sure you could get just ONE R9 295X2…but why not get a pair for Quad GPU CrossFire?
PC gamers. We do some dumb shit sometimes. Those on the outside looking in, forced to play on static hardware with fixed image quality and low expandability, turn up their noses and question why we do the things we do. It’s not an unfair reaction, they just don’t know what they are missing out on.
For example, what if you decided to upgrade your graphics hardware to improve performance and allow you to up the image quality on your games to unheard of levels? Rather than using a graphics configuration with performance found in a modern APU you could decide to run not one but FOUR discrete GPUs in a single machine. You could water cool them for optimal temperature and sound levels. This allows you to power not 1920×1080 (or 900p), not 2560×1400 but 4K gaming – 3840×2160.
All for the low, low price of $3000. Well, crap, I guess those console gamers have a right to question the sanity of SOME enthusiasts.
After the release of AMD’s latest flagship graphics card, the Radeon R9 295X2 8GB dual-GPU beast, our mind immediately started to wander to what magic could happen (and what might go wrong) if you combined a pair of them in a single system. Sure, two Hawaii GPUs running in tandem produced the “fastest gaming graphics card you can buy” but surely four GPUs would be even better.
The truth is though, that isn’t always the case. Multi-GPU is hard, just ask AMD or NVIDIA. The software and hardware demands placed on the driver team to coordinate data sharing, timing control, etc. are extremely high even when you are working with just two GPUs in series. Moving to three or four GPUs complicates the story even further and as a result it has been typical for us to note low performance scaling, increased frame time jitter and stutter and sometimes even complete incompatibility.
During our initial briefing covering the Radeon R9 295X2 with AMD there was a system photo that showed a pair of the cards inside a MAINGEAR box. As one of AMD’s biggest system builder partners, MAINGEAR and AMD were clearly insinuating that these configurations would be made available for those with the financial resources to pay for it. Even though we are talking about a very small subset of the PC gaming enthusiast base, these kinds of halo products are what bring PC gamers together to look and drool.
As it happens I was able to get a second R9 295X2 sample in our offices for a couple of quick days of testing.
Working with Kyle and Brent over at HardOCP, we decided to do some hardware sharing in order to give both outlets the ability to judge and measure Quad CrossFire independently. The results are impressive and awe inspiring.
Specifications of Performance
Let’s talk quickly about the specifications and raw power found in this kind of setup. With a total of four Hawaii GPUs amongst the two R9 295X2 graphics cards, we have a total of 11,264 stream processors at work capable of 23 TFLOPS of theoretical compute power! Between all GPUs there is 16GB of addressable GPU memory, more than most enthusiasts’ desktop system memory capacity.
With each R9 295X2 claiming a 500 watt TDP, we are looking at 1000 watts of power draw from the GPUs alone in this machine and in my testing it actually exceeds that.
Moving past the concerns of cost, which is plenty large enough on its own, power consumption issues cropped up. Our standard GPU test bed uses a Corsair AX1200i power supply that has been more than enough for our single, dual and triple graphics card testing over the last year or so. As we quickly found out though, the pair of Radeon R9 295X2 cards were able to bust past the limits of this PSU requiring us to be more creative.
Since we did not have any power supply available above 1200 watts (yet), we went with the ol’ double power supply trick. The Corsair AX1200i powered the motherboard, platform, SSD and primary graphics card while we attached a secondary Antec 750 watt High Current PSU to power the second R9 295X2. By shorting out a couple of pins in the ATX connection you can power on the PSU without it being attached to a motherboard and this allowed us to maintain a stable and functioning test system.
Clearly this is not ideal for consumers and no one should have to use two different power supplies to get a single machine running. Corsair did ship us one of the upcoming AX1500i units that will have no problems with the pair of R9 295X2 cards. However, we did not get it in time for this publication. Extreme gaming calls for some extreme power supplies, it seems.
As for a system build using a pair of R9 295X2 cards you need to find a case that can handle the mounting of two individual 120mm radiators, likely one on the back and one up top. If you plan on water cooling your CPU as well you’ll need yet another mounting location.