Chosen Solution
Looking at a picture of the internals of my 27" i7 iMac (aka my desktop background) it would appear that the SD card reader is a tiny board by itself underneath the optical drive. Does anyone else share my thought that it seems likely that the new SDXC card reader from the 2.93GHz i7 27" should be a direct replacement for the SDHC card reader in the 2.8GHz i7 model? SDXC is a pretty exciting new format, and was curious if the first i7 model had it when I first read about it in the new Mac mini. Now it’s clear that I don’t, and in a few years when SDXC takes off and I feel like installing a bigger hard drive, I want that card reader too!
It’s worth a shot. It will probably work since Apple probably only revised it to a more SDXC friendly controller. You can see the guide here. iMac Intel 27" EMC 2309 and 2374 SD Board Replacement