I thought the Cairnsmore1 used 4 heatsinks, 1 fan?
It does - one heatsink per chip, all cooled by a single fan blowing air downwards onto them.
Mmm, so it does. I should have looked more closely at the pics.
To use a different example then, the Radeon GPUs use a single heatsink block to cool quite a few different chips, with "thermal pads" used to help insure firm surface contact and transfer of heat.