I am just about ready to power up my 486 project and my first IBM machine: a PS/1 model 2155. I am waiting on a CPU for it and that is in the mail.
The service manual says this shipped with 128K of standard cache, four chips. Two empty banks are there for a max of 256K . Assuming I can get this to boot, my question is about location U19 on the main board that is listed as " Cache Memory Socket (for address module) 128K/256K" should there be anything in this location?
At present, all of my cash cache is empty...no K.
There is also mention of a "TAG" in the manual, I have no idea what this is:
"If you are installing cache memory in a board with no cache memory previously installed, install 128K or 256K as follows:
Bank 1 Add four 28-pin modules: 32K × 8, 25 ns SRAM (for 128K or
256K).
Bank 2 Add four 28-pin modules: 32K × 8, 25 ns SRAM (for 256K).
Tag Add one 28-pin module: 32K × 8, 20 ns SRAM (for 256K) or
8K × 8, 20 ns SRAM (for 128K)."