Re: PC graphic adapters on Mac Hardware
On Mon, 2003-08-04 at 11:26, Jeroen Roovers wrote:
> On 4 Aug 2003 at 10:24, Sven Luther wrote:
>
> > Because nobody has taken the time to do it ? Or if they did, which i
> > believe is true, they have not cleaned up the patch and submitted it.
> > At least for X, as said, the fbdev cause other problems, and i doubt you
> > would get an x86 emulator into the kernel.
>
> Hey, the x87 emulator is there already! Aren't there PPC forks that
> would allow for this? You wouldn't get an x86 emu into Linus's
> kernel, but it shouldn't be too hard to get it into alternative
> kernel sources, would it? Using cheap x86-compatible PCI cards was
> one reason I decided to buy a Macintosh and to run Linux on it. Any
> help is appreciated! :-)
It's not that simple.... The emulator exist, though it would be best to
have it run either in userland (from an initrd ?) or from a bootloader
than building it into the kernel.
HOWEVER, there is still a simple issue preventing using such an emulator
with a variety of cards on most Macs: The PCI Host bridge on Macs isn't
configured (and in some cases cannot be configured) to pass the legacy
ISA memory cycles used by a lot of this x86 shit to do text mode. That
is basically the "VGA memory hole" isn't accessible. If the BIOS of the
card is able to fully initialize the card using only the normal PCI
BARs & eventually a few ISA IOs, that's ok, but if it needs some access
to ISA "memory" cycles, like tapping C00000 etc..., you are dead. And that
is usually the case... It _might_ work if the BIOS sort-of emulates that
area with RAM, though it may cause problems if the card's HW is "using"
that for more than just text mode buffer...
What we would need now is for somebody to port uBoot's emulator to some
userland app in Linux, and actually try to see if we can get an x86
typical Radeon card to boot in a Mac or not...
Ben.
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