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Things didn't start off too well for the 5970 as we put it through its paces in the only DX11 game we've currently got running; DiRT 2.
It was hitting 40fps with absolutely everything up as high as it could go, at 2,560 x 1,600 with 4x anti-aliasing, which is no mean feat.
Not bad, but then slotting in the little brother Radeon 5870 at the same exact settings and, while the framerate did indeed drop, it wasn't what we expecting. The 5870's performance dropped by only 0.2fps.
Then, after loading up Resident Evil 5's benchmark, things got even worse. Not in performance terms, oh no, we couldn't actually get far enough into the benchmark without it crashing the system to get a full test in.
Poor driver support
Now it has to be said these issues are probably not down to the silicon, indeed our other benchmarks bear out the 5970 as the fastest graphics card in the world.
What it does show is, for all the tightening up of drivers on AMD's behalf, it's still tough to trust a multi-GPU setup, especially on the latest gaming titles.
The Nvidia-centric Resi 5 can be forgiven, but DiRT 2 is fully AMD'd up as a DX11 title and that's tougher to excuse.
Later drivers will shore up the problems we've found, but you can't help feel the spectre of multi-GPU cards past looming over your shoulder as you try to boot up a new game.
For your £570 you may well be getting the fastest card in the world, but you might also be buying yourself a two week wait after a new title comes out before your multi-GPU beast will have drivers that can cope with it.
But, like we said, the benchmarks we did get out of it support the fact that it's the fastest graphics card in the world (we're sorry, that's the last time we'll say that, we promise).
Against the 5870, the current fastest single-GPU card in the world (c'mon, that's a slightly different phrase...) it gets between a 50-55 per cent speed boost which is quite impressive.
AMD is also touting the 5970 as the overclocker's card, claiming it has some ridiculous headroom for tweaking its nuts off.
Overclocking potention
Now our experience of GPU overclocking has had variable results in the past, but the 5970 really does have a lot to give.
In order to keep the peak wattage below 300W AMD limited the card to a 6-pin and 8-pin power connectors, with the PCI-e bus included that amounts to 300W available to the card. With a decent PSU though we can crank that up closer to the 400W mark that the reference cooler has been designed to handle.
On the PCB there are two extra pins available to turn the 6-pin into an 8-pin socket but AMD is saying that we won't see cards with twin 8-pin connectors before Q2 2010. So we'd guess that's when we'll see the proper overclocked versions hit. Just in time to give Nvidia's Fermi cards a little scare then maybe...
All this means then is that if you get hold of a third-party tweaking tool like RivaTuner or MSI's own Afterburner then you can bump up the GPU voltage and unlock a whole world of core and memory speed headroom.
With some fairly low-level tweaking we managed to get well over 900MHz on the core and 1.2GHz on the memory side. This gave us an 80 per cent boost over the 5870 on Far Cry 2 and a massive 93 per cent increase in our DX11 Heaven benchmark.
That said you will have to put up with a noisy ol' reference fan and one hot-as-hell card roaring away inside your machine.
Our experience with the overclocked 4870x2 though still leaves us curious as to whether the increased heat and power will quickly cook the card like it did with its multi-GPU predecessor.
Massive numbers
When you're getting performance results like that then the 5970 becomes more of an appealing prospect. Once the clocks get above the 5870's stock settings then you can really see the value (and we hesitate to use that word) in this multi-GPU setup, and why it's seen as more than just a 5870x2.
But should you buy one? Well, if powering a couple of 30-inch high-res gaming screens is what you're after, and money has never been an object, then you could maybe consider the purchase.
Hell, you may even be able to hire your own personal coder to develop private drivers when it fails to run a new game...
For the rest of us though it's a step too far. The original 5870 is a pricey beast, with the more reasonable 5850 a better bet for DX11 gaming, so the 5970 is just the GPU equivalent of a £1,000 CPU. Great if you never had to ask about the price, but not so much better as to make it a must.
