I think old world Macs always booted in 640x480x8, but new world can boot at a higher
screen resolution setup in NVRAM. The change in modes to 640x480x8 maybe for compatibility
with Old World Macs.
I think reduced ATI ROM’s, that we removed the ‘NDRV’ so it would fit on a 64k EEROM
always booted at 640x480x8 until the disk based “NDRV’ loaded. I don’t think anyone ever
flashed a reduced Rage128 Pro ROM without the ‘NDRV’ sos I don’t really know how a new
world Mac would handle that, if it could still set a higher screen resolution.
Maybe we can we can get some info from the sources of the linux r128 driver?
On Jul 25, 2019, at 5:53 AM, BALATON Zoltan
On Thu, 25 Jul 2019, Jd Lyons wrote:
Sure, that's what I use for register reference all the time (and is linked from my
qmiga.osdn.io page although not directly to avoid possible copyright problems but the card
page where the doc is available linked and I've told you that before and also hinted
on that page. There are more docs available from the pages linked from my qmiga page, all
those might have useful info (the prg and sdk guides too, even though they are for
different cards but these are similar so some details are the same).
However it does not explain what AMCGPIO is, only what are the bits in those regs or did
I miss that part where it actually says what should be accessible via that register? From
the access pattern it looks similar to GPIO_MONID where we have the EDID so maybe the card
has another connector the DDC/EDID of which is accessed via the AMCGPIO reg? The FCode
checks both but switches mode after reading AMCGPIO and before getting EDID from
GPIO_MONID so maybe we need to add EDID to the AMCGPIO reg? But I don't know which
bits to connect it. Probably one could find out by reading the detok-ed FCode source to
see what it does with the EDID and how does it select mode or find an open source driver
that accesses this to find out how this should work.
But the problem currently is with the offset 8000 in the selected mode which the QEMU VGA
emulation can't handle or I don't know how to make it handle. That's why
picture is wrong at the moment. So either we should allow this offset or find out why
FCode wants that and when it uses different mode is that better aligned then? Where does
it get this 640x480x8 mode and shouldn't it use something higher by default? I
don't know how MacOS works and what its default mode is.