This is an upgrade CPU module that plugs into the 286 processor socket in IBM PS/2 50z systems and upgrades them to a 486SLC processor with on-chip cache. It also adds a secondary socket for a 387 floating point processor.

I bought it intending to upgrade one of my 286 systems, but none of them I've tested with will work.

It seems that there is some glue logic that means it only works with certain PS/2 motherboard models, and not generic systems.