Hi tony, Yes, they are Mostek - and I recall the stacked 4164's in the IBM AT - I just posted that they were 4116s, but thats due to bad bits in the organic memory array - you just reminded me that they were 4164's - allowing 512K on the 256K board - ahh the days of such huge capacity... It does appear that this is what these things are ... IIRC, there was a similar stacked arrangement for SRAM chips in the Radio Shack (Kyocera) Model-100 - the "8k" device was actually 4 x 2k devices on a small carrier - problem was that they brought out the 4 selects instead of address lines, so you couldn't just put in an 8k device - I bought a third party RAM chip which had an 8k device on a small board with some diodes to generate a common select (the extra address lines must have been there as well, because there was no other logic on the board) - seemed a skunkwork design to me, however it never gave me trouble (in fact it's still working). What wonderful little things get created to fill in the "gaps" in available devices... Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.parse.com/~ddunfield/museum/index.html