If it was built for 486SX, you could probably run stock NetBSD decently on this system with performance not much different from when the system was new. Edit:

If it was built for 486SX, you could probably run stock NetBSD decently on this system with performance not much different from when the system was new. Edit: Looks like you would be able to do a customized low-memory/disk install of NetBSD 7.1 on these systems if they had an FPU (either a full 80486 or an 80487 coprocessor). With 32MB RAM and 250MB disk in addition to the FPU, you wouldn't even need to do a customized install.