OK, in this thread I'd like to posit something that i have been mulling over in my mind for the past week. Before the latest round of updates, we had 2 AL iMac models, the 20" and the 24". We knew that the 20" has a separate motherboard design and cannot accept a different graphics card. But the 24" could, via the MSM slot, and provided it was a mac version. For example, if you had a 2600 PRO and wanted to upgrade to an 8800GS, you could provided you took the damn thing apart to get at the card. Now with the new iMac generation, they seem to be all based on the NVIDIA MCP79 chipset and that includes an integrated 9400M GPU and in the higher end 24" you have discreet GPUs. We still have the 20" with it's own motherboard and it will not accept a GPU. But I suspect that the low end 24", the one that is advertised with a 9400M integrated graphics, has an empty MXM slot. My reasoning is that if it doesn't then Apple has to make 3 different motherboards for the iMacs when it would make more sense to only have 2 and install graphics cards into BTO models and the discreet graphics retail models. And it's highly unlikely that the motherboard for the 20" was put into the lower end 24" because these motherboards are not square PCBs but a form fitted and cut to fit around components in the case. We'll only know for sure when there is a take-apart for it. So far I've only seen 20" take-aparts.