I was saying that NetBSD works on those older systems, while it either has no support (64-bit POWER) or spotty support (modern ARM) on more modern platforms. I've got netbooting set up for all of them, and it's "useful" for testing, though even a 20 MHz VAX is pain and suffering (12+ hours to generate RSA private keys for SSH).

FWIW, Linux does work fine on the Alpha, it's just slow. Both NetBSD and Linux have busted framebuffers on my workstation, which has a 3DLabs graphics chipset. Having acceleration enabled causes Linux to output pure garbage, and NetBSD to kernel panic. The CPU performance is surprisingly okay, though. About half the performance of an original Raspberry Pi, in pure integer math...

Linux is busted on my SPARC box though, not because of the system itself, but a bug in the Weitek 2000A CPU. It was an aftermarket part from Weitek, and in order to retrofit an 80 MHz CPU into a system with discrete MMU and cache chips that expect a 40 MHz single-issue RISC processor, it adds a funky on-chip cache, branch-predictor, and instruction prefetcher.

Details on specifics are ~impossible to find nowadays, but the word on Usenet was that chips made before 1995 are no good for Linux. My limited testing with a '93 chip corroborates this. I really ran into this while building a new Sprite [0] distribution, where I learned this chip makes tons of spurious page faults from the branch predictor hitting bogus instructions, which causes the Sprite (and Linux?) kernel to freak out. This corroborates the Usenet reports for random signal 11s killing processes on Linux...

Doesn't effect NetBSD, though. I think this [1] code is why (replaces the bogus fault address with the process counter) but I'm not sure. I have a partial fix for Sprite's kernel which allows userspace to boot up and work, and have networking fixed, but if you sneeze it kernel panics and murders the Sprite-bespoke filesystem, so testing has been a slog. :-)

[0] https://en.wikipedia.org/wiki/Sprite_(operating_system)

[1] https://github.com/NetBSD/src/blob/trunk/sys/arch/sparc/spar...