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
dlachausse•6h ago
Very cool project!
actionfromafar•6h ago
What this NetBSD project does is not exactly like that though, it lets programs use regular 487 float instructions, which are trapped by the kernel, which steps in and emulates what the hardware float instruction would have done.
It worked very well for regular program, because most programs would not use float instructions to any significant degree.
If you however were going to use floats a lot for long calculations, a soft-float library would be much faster.
queenkjuul•5h ago
At least this is my impression, working with 2.2.x/2.4.x kernels, gcc 2.7~3.3, and glibc ~2.2
anyfoo•5h ago
The benefit of OP’s solution in the kernel is that it works for everything out of the box, including pre-compiled binaries, and those that you can’t rebuild for whatever reason to begin with.
rasz•1m ago
It just so happens first room when starting the game - rooftop - has sloped roof vents and later walls with sloped edge. Even on fast FPUless 90MHz NexGen Nx586 (AMD K6 father) FPS drops down to 10-14fps on that roof https://www.youtube.com/watch?v=41O2bNG2qKA&t=234s while staying above 30 when facing away from slopes.