Canon cameras make a big thing about how they use a custom Canon designed ASIC called DIGIC. One of the features mentioned is "faster processing converts RAW data to JPEG image in buffer". They've had several revisions of this chip now and it is used from the P&S cameras up to the big DSLRs.

Since the DIGIC chip does receive the raw data from the sensor then it should be possible in theory for somebody to hack the firmware to reenable this feature on cameras which don't support it. All the Canon cameras I've seen run an embedded variant of DOS on a 80186 clone. The Digital Rebel/300D crowd are/were big into hacking firmware to reenable features.