I was looking for documentation on which memory slot is which in the white (flat screen) iMac. System profiler doesn't really say other than DIMM0/J12 and DIMM1/J13. Since one is not user accessible and one is it seems that the internal slot might be 0 and the external 1. Alas it appears that it is the opposite. DIMM0/J12 is the SO-DIMM PC100-2225 ram that users can access and upgrade.