That is precisely my experience w/ my chip which has L2=512. Although the system BIOS will recognize 512 MB of RAM it will run much better (faster) w/ 256 MB and NO stability issues. I was expecting big things with the second 256 MB. Alas, no joy. By the way 384MB performance is good too. I just used the 128 MB stick in another box or I would have reinstalled it w/ the 256. All memory is matched for CAS (2) and Manufacturer. YMMV