Re: [hatari-devel] Possible bug in 060 exception stack frames

[Toni Wilen <twilen@xxxxxxxxxx>]

>  > Yes, I tested it with real 68040, those 3 instructions won't modify
>
>  > FPIAR.
>
> Thats strange and does not make much sense to me, especially because it 
> apparently only affects 040. I'll see whether i can update the test 
> program so it does not report failures for this when run on 040.

68881/68882 also does not update FPIAR in this situation.

FPIAR behavior has changed between 6888x and 68040/060.

68881/2: FPIAR is only modified if instruction can generate arithmetic 
exception and at least one arithmetic exception is enabled in FPCR. This 
is also mentioned in 68881/2 documentation.

But 68040 and 68060 will always modify FPIAR if instruction can generate 
any arithmetic exception, even if arithmetic exceptions are disabled. 
FPIAR is also modified if instruction generates non-arithmetic exception 
that 6888x does not generate, for example if instruction or addressing 
mode is unimplemented (that is implemented in 6888x).

I can't be 100% sure but so far this seems to match real hardware behavior.