See here's what's funny. Most people agree that the 580 isn't in high quantities, but it's an enthusiast card so it doesn't matter...
And yet, they aren't selling out despite having low quantities, in a buying season, and when they're targeted at enthusiasts who are going to snatch them up anyways regardless of price...
So why does AMD need to worry again?
Simply keeping Cayman under wraps is creating confusion amongst buyers. Yes, it annoys them, but it keeps a lot of the non-fanboys from jumping to Nvidia simply because there's something out around the corner. The fanboys have snatched up the first cards, but now the other buyers wait... which means Nvidia isn't getting those sales yet.
Yes, if AMD were delaying 6+ months like Fermi, there'd be a legitimate beef for AMD not giving numbers. But that's not the case - it's less than a month's delay and it apparently isn't hurting seeing as how 580 isn't plentiful in many places in Europe, and what's available in America isn't selling out either
And ever since R600, AMD has kept their lips sealed on whats coming. You know what other card was a big unknown and was stunning despite being quiet up to release? RV770. And since RV770 was 2 gens ago, and AMD has adopted a tick-tock strategy with their GPUs, this silence probably suggests a good thing
Bookmarks