Atari's own part number for 64K DRAMs is CO60612, but not many machines actually have the CO60612 on the dips. I've seen all types of OEM names like 4164, 4264, 4564, etc. What specs are required to be used in an XL/XE? I'm wanting to buy spares. I ordered some CO60612s from Best and Brad send Mitsubishi 4164s. I'm sure they will work, but just want to know what the requirements are or what specs to avoid when selecting a 64K x 1 DRAM.