Thanks, Bruce, for the NetBSD 1.5.2 test kernels, but they hung just like
NetBSD 1.5.1.  So did NetBSD 1.5 generic kernel.  CPU chip calls itself
Cx486DX2-S at 66 MHz in the BIOS screen on boot-up, but NetBSD calls it
Cyrix 486DLC.  I don't know if that makes any difference.  So that gives me
another idea of what OS is "about as stable as the elements at the bottom of the
periodic table".  Sorry about that!  Maybe a candidate for a bug report?

OpenBSD floppy29.fs booted, but OpenBSD has no support for my SCSI, to which the
internal CD-ROM drive is connected.  Linux boots some of the time, depending on
which kernel and root-disk combination, but hangs if I attempt to mount the
CD-ROM.  If I want to install something besides DR-DOS 7.03 on this computer,
Linux seems to offer the best hope, though I might have to see if I can debug
the NCR5380 SCSI module.  Since I will be buying a new computer, there is not
really much point in installing anything besides DR-DOS 7.03 on the old computer
at this stage.