Re: MiNT and FPU problems

[Jo Even Skarstein <joska@nuts.edu>]

On Tue, 6 Oct 1998, MGrove wrote:

> Last weekend I reinstalled a Nemesis in a Falcon/Mighty Sonic setup.
> For some strange reason under MiNT and N_AES, launching any 
> application that utilizes the FPU causes a MiNT error. "Coprocessor 
> protocal violation". I removed autofolder app's and acc's to see if it was 

I had this problem when I first installed Nemesis in my Falcon (no
AB). If the FPU was double-clocked, MiNT would halt with a
"Coprocessor protocol violation" during boot when the Falcon was
running at 20/40MHz. At 24/48MHz it worked fine. If the FPU was not
double-clocked, MiNT halted at 24/48MHz but worked at 20/40Mhz. Very
strange indeed...

I solved this problem by removing the FPU-acceleration and clock the
FPU separately with a 50Mhz clock (same as DSP). This worked fine for
two weeks, then I got the AB and had to remove the 68882 anyway.

I had a brief look at the MiNT-sources, but couldn't find out exactly
why this happens. I can only assume that MiNT performs a check or
catch an exception that TOS ignores.

Btw. while the FPU appears to work fine under TOS and not MiNT, I
remember having problems with the FPU under TOS as well. E.g. if I ran
multiple test over an hour or so, the Falcon would eventually lock up
during the FPU-tests. So my guess is that this is purely a
hardware-problem, and not a MiNT-problem.

Cross-posted to the MiNT-list for comments.


/*
** Jo Even Skarstein    http://www.stud.ntnu.no/~josk/
**
**    beer - maria mckee - atari falcon - babylon 5
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