SPD spec on Wiki

http://en.wikipedia.org/wiki/Serial_presence_detect#SDR_SDRAM

Check Offset 5: memory type (SDR SDRAM/ DDR SDRAM/ DDR2 SDRAM/ DDR3 SDRAM)

Check # of banks

Check module bank density (512Mb, 1G so on)

DIMM size = module bank density x # of banks