exxos's Atari, Amiga & retro forum

exxos wrote: 04 May 2025 20:39

Steve wrote: 03 May 2025 22:12 Yeah I do a lot with MiNT which require an FPU to work properly.

Oh, anything in particular ?

Pretty much all of it, even the most basic programs, they're compiled to require an FPU.

Steve wrote: 04 May 2025 21:43 Pretty much all of it, even the most basic programs, they're compiled to require an FPU.

ahhh ok. Wasn't that when someone was talking about it just "looks" for the FPU but never actually uses it though ?

Can you make a daughter board that plugs in to the CPU socket for it?

PhilC wrote: 04 May 2025 22:21 Can you make a daughter board that plugs in to the CPU socket for it?

That probably be more work than a respin of the board... Plus with all the hassle with the FPU on the DFB1X id likely not risk it either. At 50mhz everything has to be as good as possible else it won't work.

exxos wrote: 04 May 2025 21:44 ahhh ok. Wasn't that when someone was talking about it just "looks" for the FPU but never actually uses it though ?

Whether it uses the FPU or just looks for one is kind of redundant, because there's literally hundreds of programs that make up MiNT (unix programs that boot from the kernel etc) So even on boot-up it might invoke a bunch of stuff that checks for an FPU. Like even the disk check which scans the disk for errors after an improper shutdown, even that won't run. FYI there was a big discussion here on this forum about the issue, I think Mikro was mainly involved in the discussion as he's the main maintainer of mint these days. As far as I'm aware it's not thought of as a bug, and it's always going to stay that way. There *is* the possibility of including an FPU emulator in Mint builds, but Mikro is concerned that it would slow down the distribution and cause lots of people submitting bug reports for 'slow FPU'.

@Steve Sounds like a FPU may just be a good idea if it causes that many headaches in not having it. I never considered mint, though I never used it.. aside from maybe last year where I just got a sh*t ton of errors, so gave up :P

FPU List ...

https://www.atari-forum.com/viewtopic.php?t=40575

The current 68030 versions of the MiNT libraries seem to be built using GCC with the m68882 support switched on and the start-up code (crt0.o) checks for an FPU and crashes out if it's not found.

This is very silly and I have no idea at what point this was set-up, as it wasn't there when I was actively helping the MiNT system in the mid 90s. It was probably someone's bright idea assuming that the only 68030 Atari hardware to ever exist would be the TT and Falcon (upgraded with FPU). To be honest, there was no reason to code it this way, you just have two versions of the libm library if you want software or hardware floating point.

So looking at the list of uses, I don't think I would have much use for an FPU, other than using up one of my spare 68882 chips.

Anyone who has ever tried to make an 030 accelerator card will tell you that the FPU makes the timings much much worse so if you want a stable working board lots of care has to be made with the layout.