BSD on vintage computers

Intro

Current BSD distributions consume much more CPU power as its predecessors 20 years ago.
Modern BSD versions don't support 486 processors without mathematical co-processor anymore (e.g. an UMC U5S).
Vintage BSD distributions have often a better support for elder graphic cards (e.g. by using XFree86 in the version 3.3.6).
The disadvantage of using elder BSD's: you can still download it but the hints how to admin such a system are nearly lost (or better: overwritten by the newest stuff).

OpenBSD

Version 6.4 boots on an AMD 5x86-P75 (Am486DX4-133) only, all other 486 from Cyrix and AMD crashes immediately after the bootloader. I sent a bug report and Jonathan Gray fixed it within one day! Thank you very much for this work again!

Version 6.5 runs out of the box again. OpenBSD still has a floppy image for computers which can't boot from a cdrom drive.

After installation I switched off nearly all demons in the rc.conf.local to save CPU power. The relinking of the kernel is a nice feature for current CPU's but for a 486 is it a 20 minutes full time task after startup. We can comment it out in the rc file because I can't believe you are using a 486 as a 24/7 internet server...

NetBSD

The version 9.0 runs on the 486 platform but the standard kernel (also the installation kernel) doesn't support ISA graphic cards anymore. You must install NetBSD on a motherboard with a (at least) PCI-bus graphic card. After successful installation:

save the installed kernel (e.g. mv netbsd netbsd.gen)
copy the LEGACY-kernel into the root (/) directory (the installation CD-ROM contains also this kernel)
unpack it with 'gunzip netbsd-LEGACY.gz'
rename the file: mv netbsd-LEGACY netbsd
I gave the new kernel the same mode as the old one: 'chmod +x netbsd'
reboot into your good old ISA system...

Some interesting vintage versions:

Version	Remarks
1.5.3	Last version with XFree86 3.3.6, support for 486SX (without floating point unit)
1.6.2	Last version without ACPI and SMP (symmetric multiprocessing)

FreeBSD

FreeBSD version 12.0 doesn't start on my 486 boards anymore (crashes immediately after the boot loader). Depending on the chipset it happens on some socket 7 boards also. At the moment I haven't investigated this topic yet.