I keep acquiring strange machines and I have turned my attention to a NCR 3220/3221:

This is a 486sx 20mhz microchannel machine with 3x 16 bit slots. Other specs include 8mb ram, SCSI, and a very jaunty icon for the mouse connector.

The power supply is dead, but the connector is AT pinout so I am powering it with a ATX->AT adapter while rebuilding the original power supply.

I was able to scrape the NCR site in Wayback so I have copies of the ref disk and drivers. The included hard drive works, but unfortunately the ref disk/drivers on the hard drive are the same version as I downloaded from NCR.

Finally, the floppy only has a 34pin connector. I guessed that it was media select and was able to get my Gotek working with the same adapter I used on my PS/2 76.

However, the point of this post concerns the CPU card:

A 486sx at 20mhz is not exactly snappy and I have plans involving MCA video capture boards, so I would like to upgrade the CPU. I don't have much experience using overdrive sockets, but I have two CPUS on hand, and neither worked in the socket: a DX2 66mhz and a Gainbery - some sort of Cyrix processor with interposer. I cannot be certain that either CPU is functional. My understanding of the 487 sockets is that you can use a standard DX processor - the extra pin is to prevent using a cheaper 487 processor in a standard 486 socket?

Any thoughts?