I am not sure if you guys all missed a previous post where I said I
found a reference that there are issues with some SMM BIOS
implementations, providing legacy USB support (for keyboard and mice)
and software that is trying to switch in "long mode" (which also might
be used by some memory managers).
Which could simply mean that this no-so-PC BIOS in that Mac just isn't
up to snuff for these kind of things...
Ralf
On 11/14/2020 4:34 AM, Eric Auer wrote:
Hi!
I like TK Chia's idea that DOS/16M tried to access the
keyboard controller to change A20: It would probably
stop doing that when HIMEM and/or EMM386 are loaded,
but having a DPMI loaded can be even more convincing.
Same for DOS4GW: If A20 control is already provided by
something else, or protected mode is already being used,
it is less likely to try to change the A20 itself.
For PC, the BIOS tends to trap I/O to the controller
so even USB keyboards can behave like real ones, but
your iMac / rEFInd / CSM probably do not do this.
You can still try whether one of the CTMOUSE versions
is able to use the mouse via PS/2 BIOS calls with some
suitable command line options. May depend on the model.
VGA + VESA (graphics) works. It's discovered VESA 3.0 with LFB
Quite nice :-)
Sound card related experiments are still in front of me
Expect only a few modern media players like MPXPLAY to
support AC97 or HDA at all. If you want soundblaster
compatibility, you would have to use emulators. There
seems to be a DOSBOX-X version which can run inside DOS
which might help with that, but the normal way would be
to use Windows or Linux with DOSEMU2 ;-)
Regards, Eric
PS: No idea whether your CSM is rEFInd provided, Apple
provided or from somewhere else. If you would know, you
could simply read docs instead of testing it's features.
Maybe some strings at f000:0 to f000:ffff give answers?
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