I just had a look at the disassembly photos posted on the japanese site https://www.macrumors.com/c.php?u=h...s/2007/08/aaaaaaaaaaaaaaa_3.html&t=1186652702) and it looks like the GPU is on an MXM! Of course this needs to be confirmed but the layout and the size of the socket suggests it to me. Pitty the heatsink is connected to the cpu one, but what else could they do?