What's a Radeon HD 5970?
While the HD 5970's two Cypress GPUs each have the full 20 cores enabled (for a total of 3,200 stream processors in the card), both the memory and core clocks have been reduced fairly significantly. The card's clocks are actually in line with those of the Radeon HD 5850, with a 725MHz GPU and 1GHz (4GHz effective) for the 2GB of GDDR5 memory. Bear in mind that the HD 5850 only has 18 of the maximum 20 cores are enabled, so it's incorrect to say that the HD 5970 only has a pair of HD 5850 GPUs.
For those not familiar with the Radeon HD 5000-series architecture, we recommend ploughing through our Radeon HD 5870 architecture analysis
, because it covers everything you need to know. Of course, everything is doubled up on the Radeon HD 5970, meaning 640 five-way superscalar shader processsors, 160 texture units, 64 ROPs and two 256-bit memory interfaces that each lead to 1GB of GDDR5 memory, making that 2GB total .
Taking all of this into account while we reach for our calculator gives the HD 5970 a roughly 70 per cent improvement in raw throughput over the Radeon HD 5870. Compute performance stands at a whopping 4.64 TeraFLOPS, texture fillrate is an equally impressive 116 GigaTexels/sec, while it'll push almost 50 million pixels per second (well, 46.4 million to be exact). Memory bandwidth breaks through the 256GB/sec barrier for the first time, too - every which way you look at the HD 5970's specs, you'll come away impressed.
What's not so impressive is the fact that in order to house this amount of power, our worst nightmares have come true. No, it's not the fact that it's another addition to the Batmobile family - it's because the card troubles the tape measure at
12.2in long. This means there are only a few cases that the card will actually fit in without modification.
Thankfully, the card still only sports both a 6-pin and an 8-pin PCI-E power connector to add to the 75W of power drawn through the PCI Express slot. AMD says that the HD 5970's maximum power consumption is 294W - this isn't exactly what we'd call frugal, and it's higher than both the GeForce GTX 295 and Radeon HD 4870 X2, which stood at 289W and 286W respectively. The good thing is that the board's idle power is lower than that of two Radeon HD 5850s at just 42W. AMD introduced some new power saving modes
that are able to shut down parts of a second GPU that aren't in use when the card is idling to help further reduce the burden of having a high-end gaming system that doubles as a work machine.
Thanks to the red and black Batmobile-style trim, the HD 5970's cooler looks very familiar from the outside, but AMD says that it has done some work to improve its cooling performance. While the fan is exactly the same as those on HD 5870 and HD 5850 reference cards, AMD has employed Sapphire's Vapour Chamber technology
to support up to 400W of dissipation. Despite this, it's no surprise that the card is very
loud under load, especially given the amount of heat coming from two Cypress GPUs. The good thing is that the cooler quietens itself down as soon as its idling and it's as quiet as any other Radeon HD 5000-series card when you're not gaming.
AMD has spent some time working on the power regulation and tweakability of the card, introducing widespread voltage adjustment for GPU and memory, and the firm effectively begs you to overclock the nuts of the 5970. Whether it's worth doing will have to wait for another day, because we were short on time in getting this article completed - we'll be following up with our board examination, some overclocking and hopefully a bit of EyeFinity performance as well.