I486SX_soft_FPU – Software FPU Emulator for NetBSD 10 on 486SX
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…
I486SX_soft_FPU – Software FPU Emulator for NetBSD 10 on 486SX launched on April 27, 2025 with 117 votes, #409 of 7,818 launches that month and more than 95% of that year's launches. The site was still online in September 2026, 1 year on.
In plain words
I486SX_soft_FPU is a software floating-point emulator that enables the classic Intel 486SX processor to run modern NetBSD 10, which no longer natively supports CPUs without hardware FPU capabilities. The tool restores floating-point functionality to 486SX machines, making it suitable for retrocomputing enthusiasts and system developers working with legacy hardware. It is open-source and available on GitHub.
written from the facts on this page · September 2026
From the sources
Bring back FPU emulation for i486SX CPU on NetBSD. Contribute to mezantrop/i486SX_soft_FPU development by creating an account on GitHub.
This retro-computing project restores support for x87 floating-point unit (FPU) emulation in the NetBSD kernel, targeting legacy 486SX-class processors without hardware FPUs. It brings back the original MATH_EMULATE option into NetBSD 10.x and beyond, as well as reverts and reworks the changes introduced in commit dfe83e0 , which removed FPU emulation support from the kernel. This project is a work in progress and may contain bugs or incomplete functionality. Use at your own risk. The author is not responsible for any issues caused by its use. $ cd /usr/src/sys/arch/i386/conf/ $ vi GENERIC_TINY_486SX# or GENERIC_PS2TINY_486SX or create your own kernel configuration with " options…from github.com
In the maker’s words, at launch
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…
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