Finally they've arrived; the much-anticipated Cayman GPU-powered HD 6900 series cards from AMD. And right here we've got the very top-end of AMD's latest single-GPU cards, the AMD Radeon HD 6970.

Now we've been waiting a fair few months for the release of these new cards, with their brand spanking new GPU, and still it's hard to see exactly why we've been waiting so long.

Originally penned in for launch just after the HD 6800 cards, suddenly we saw the launch slip back and Nvidia then spoiling a party that simply didn't exist. The Nvidia GeForce GTX 580 was brought out incredibly early, specifically to counter these Cayman-powered cards only to find they were still some months away from release.

AMD has remained fairly tight-lipped about the slippage. Some of our sources claimed it was simply down to money. AMD wanted the higher margins of the mid-range HD 6800 cards around Thanksgiving aiding its bottom line, whereas a few top-end HD 6900 cards wouldn't have given them the same cash boost.

Still, I'm sure there were a fair few people who held off buying a new card until AMD had its top-end GPUs out the door, so I'm not entirely convinced about that rumour.

At a recent briefing, though, AMD blamed the PowerTune technology in its new cards as the delaying factor. But to us that sounds suspiciously similar to Nvidia blaming the delay of the GTX 480 on the design of its Tessellation engine.

It may well be a while before we know the full story.