Question: I use K8 939 pin CPU. When I install two different sizes memory, 256 MB and 512 MB on blue DIMM slots of K8Combo-Z / 939A8X-M / K8Upgrade-1689, it only recognized 512 MB for total memory size. Why?(3/21/2005) Answer: Due to the memory sizing code of K8 939 pin revision E CPU, it will auto run at dual channel mode. The two memory modules will be recognized as the same size for both DRAM (256MB + 256MB) to run dual channel mode. For optimal compatibility and reliability, it's recommended to install identical (the same brand, speed, size and chip type) DDR DIMM pair in the slots of same color.