Hacker Remix

Show HN: I486SX_soft_FPU – Software FPU Emulator for NetBSD 10 on 486SX

108 points by mezantrop 1 day ago | 38 comments

First Release is Here!

I'm excited to announce the first release of i486SX_soft_FPU — a software FPU emulator for the classic Intel 486SX CPU, running on NetBSD 10!

This project brings floating-point support back to life for 486SX machines, even though modern NetBSD versions no longer natively support processors without a hardware FPU. If you're into retrocomputing, operating system hacking, or just love old-school hardware, check it out!

Project page: https://github.com/mezantrop/i486SX_soft_FPU Contributions, feedback, and testing are all very welcome!

Let's keep these vintage machines alive!

#retrocomputing #NetBSD #486SX #opensource

jabl 18 hours ago

Just a few days ago patches were posted proposing to drop Linux kernel support for x86 cpus lacking a FPU: https://lore.kernel.org/lkml/20250425084216.3913608-1-mingo@...

remlov 7 hours ago

Good thing this has nothing to do with NetBSD.

accrual 24 hours ago

This is super cool and I'm very glad to see such work! Does NetBSD natively support the 486DX CPUs which still have the FPU enabled?

I know OpenBSD dropped support for i486 in 6.8, making 6.7 the last that runs natively on them (FPU or not). The support was lost when moving to LLVM 9 and enabling `-march=i586 on i386`. However, old Socket 3 boards can still run the latest version of OpenBSD if one drops a Pentium Overdrive in. :)

dcassett 18 hours ago

> Does NetBSD natively support the 486DX CPUs which still have the FPU enabled?

According to [1] they do

"Any i486 or better CPU should work - genuine Intel or a compatible such as Cyrix, AMD, or NexGen."

[1] https://wiki.netbsd.org/ports/i386/

userbinator 19 hours ago

Not only the 486SX but a lot of alternative x86 SoCs aimed at embedded systems have no FPU, including the original Vortex86.

natas 21 hours ago

I wonder if this means we will soon be able to run Netbsd-10.1 (and above) on MiSTer with ao486 core.