Fancy getting your hands on AMD's swanky new Graphics Card Next (GCN) technology but don't want to spend the small fortune it costs to purchase a Radeon HD7970? Rejoice, then, for today we have been blessed with the second card in this new range, henceforth to be known as the Radeon HD7950.
Don't get too excited: it's still not what you'd call a cheap card. Retail prices have been set at £ 355 /$449 and upwards, which puts it pound for pound up against the erstwhile fastest current single chip GPU, the GeForce GTX580. So how does GCN compare to NVIDIA's best?
The HD7950 has the same Tahiti processor as the HD7970, which was released just before Christmas and it also comes with the same 3GB of GDDR5 RAM on a 384bit bus width. The only difference is that four of the 'Compute Units' have been disabled, and clockspeeds for both the processor and memory reduced.
As is common practice for all processor manufacturers, what you're essentially getting is a card which hasn't met the quality control conditions for the more expensive boards but is still fully functional across most of its silicon. Given AMD's track record for locking off disabled cores, it likely won't be long before we see people attempt custom BIOS creations that try to turn them back on again, converting a HD7950 into a HD7970. Personally I wouldn't hold out hope that you'll be able to do that, but who knows?
Since each Compute Unit within GCN's structure has 64 shader cores arranged in four batches of 16, the HD7950 has 1792 cores compared to the 2048 in the HD7970, and these are running at 800MHz by default (HD7970 has a base speed of 925MHz). What's interesting, though, is that there's no reference design from AMD – so at launch there are plenty of cards from the likes of Sapphire and HIS that are overclocked out of the box. Most seem to have settled on 900MHz as a good round figure to ship with.
The most important thing is that HD7950 retains all six of the dual channel memory controllers and the 32 ROPS of the HD7970. There's nothing to slow the card down if you're planning on running at ludicrously high multi-monitor settings or with tons of anti-aliasing on. Apparently there is a 1.5GB version in the works which will appear at a more sane price.
Personally, since I don't really need the extraordinary rendering power of a top end card for my single screen set-up, what I really appreciate about GCN is its exceptional power throttling. In a recent round up of HD7970s, a system built around a Core i7 2600K idled at just 65W. The HD7950 also inherits this ability to totally shut down unused cores on the card.
A quick scan of early reviews suggests that AMD has done very well with this launch, and consolidated its position as the vendor of choice if you want to spend lots of money on graphics. Not only does the HD7950 comfortably beat the GeForce GTX580 in nearly every benchmark, new drivers have been released which improve the performance of the first GCN card as well.
Here's what the review sites are saying:
Anandtech politely says that “the 7950 renders the GTX580 irrelevant”.
Bit-tech , however, urges caution and says that no HD6900 or GTX580 purchaser should “rue their purchase”. They're disappointed with the high price points of both GCN launches and expect better value soon. They think NVIDIA's Kepler chips will be arriving before long.
TechRadar celebrates the fact that HD7950 may ship with low clockspeeds, but “even if you've never overclocked a graphics card in your life you owe it to all the engineers who worked on the Tahiti GPU to push it north of the 1GHz mark”.
Over at Tom's Hardware , there's a complaint that the HD7950 is noisy, and that some features (like video encoding) are still flaky with the new drivers. Still, they concede “there's really no contest” when it comes to a decision to buy this or GTX580.
All positive, all couched in somewhat surprising caveats. The question now is whether or not NVIDIA can get its next generation chip, codenamed Kepler, out before all enthusiasm for it wanes. Rumours are it might turn up next month. Wait and see...