You should be able to add another two 4Mx16 SDRAM chips and caps to get a total of 32MB. However, you'll also need to write some code to (a) turn the bank on and initialise it correctly, which has to run from flash (eg, on the 0xe000 boot section) and (b) tell linux about the extra memory.

Unfortunately, I didn't have time to make it autodetect memory and autoconfigure it. That and I don't think (at the time) we had any spare chips to test such a patch

Hugo