He's personally tested it, and was the one to discover it (so I'm not sure why he says "it's been reported"). The ATi Radeon HD 4xx0 series cards (and the HD 3xx0 series cards, but to a lesser extent, I think?) offload a bit of work to the CPU, and since PCSX2 needs the most of two cores, with one of those cards paired with a dual core CPU, speed suffers quite badly in some games. Since PCSX2 can't utilize quad core CPUs (yet, and when it does, it probably won't be by too much), users who've had these cards with quad core CPUs didn't get affected by the speed drop, since the card's work was offloaded to one core, leaving two (three) free for PCSX2.
However, you're behind the times runawayprisoner. During your absence, Squall-Leonhart once claimed that that's been fixed via ATi's drivers, and quite a bit after that, this showed up.
The ATI bug has been fixed!
It'd be interesting if you could test this and see if it's truly so, but many ATi users have claimed speed gains.
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