Re: [hatari-devel] WinUAE Falcon emulation and FPU

[Thomas Huth <th.huth@xxxxxx>]

Am Mon, 1 Oct 2012 22:20:45 +0300
schrieb Eero Tamminen <oak@xxxxxxxxxxxxxx>:

> Hi,
> 
> On maanantai 01 lokakuu 2012, Thomas Huth wrote:
> > schrieb Eero Tamminen <oak@xxxxxxxxxxxxxx>:
> > > Why old UAE core emulates by default something which
> > > isn't standard on 030?
> > 
> > Because UAE means U* _Amiga_ Emulator, not U* _Atari_ Emulator ;-)
> > More precisely, it originally also did not really emulate
> > a 68030, but a 68020+FPU only, so this CPU level was rather used
> > to enable the FPU for 68020 in the old UAE core. But since some
> > people complained about that a Falcon rather needs a 68030, we
> > upgraded it to 68EC030+FPU at one point in time :-)
> 
> I was more of asking can it be turned off and if yes,
> shouldn't we turn it off as normal Falcon doesn't have an FPU?

That's what I was trying to say, with old UAE core, you've got to
switch to the plain 68020 CPU level to run without FPU.

You really can only configure the CPU core the way that is currently
reflected by the GUI. Either 68020 or 68020+FPU (aka. 68EC030+FPU).
Nothing more, unless you start hacking the old CPU core. But that's not
worth the effort, our ultimate goal should rather be to fully switch to
the new core instead.

> Hm.  Now I started to wonder is it possible that
> there's something that does NOT work in presence
> of FPU, e.g. because it detects FPU, but its FPU
> support is broken...

Theoretically a program could use the Line-F trap to call internal
functions. Such a program would not work anymore when an FPU is
suddenly available. But apart from the very early TOS 1.0x ROMs, I've
never seen a program that abuses the Line-F trap this way.

 Thomas