[B2-devel] MMU stuff

[<ni...@in...>]

I wrote:
> > [NetBSD/mac68k booter]
> > I am the maintainer of the program
> 
> Are you also the maintainer of the NetBSD/mac68k Installer?

	No. There hasn't really been a maintainer of it for years.
They are trying to move away from the installer, though, toward
a "sysinst" kernel based system.



> The byte at 0xcb1 holds the MMU type:
>   0: None
>   1: AMU
>   3: 68851
>   4: 68030
>   5: 68040
>   6: EMMU (PowerPC)

	Didn't work for me.

1) I just had a look at some documentation,
   (MacPerl's LowMem.pm, and LowMem.h from Apple's Universal Headers)
   and it seems that 0x0CB2 is the address. 0x0CB1 appears unused

2) Doing this:

   (* (unsigned char *) 0x0CB2) = 3;
   printf("mmu=%ld\n", GetGestalt(gestaltMMUType));

   in a MacOS program still outputs 0.

3) Fiddling around in emul_op.cpp, changing this line:

   case M68K-EMUL_OP_PATCH_BOOT_GLOBS;
   ...
        WriteMacInt8(r->a[4] -26, 0)			// No MMU

   to write 1 gives me mmu=1, but 2 gives 0,
   and 3, 4 or 5 cause the Mac emulation to never boot.
   (haven't investigated why)

4) I had a look at the InitMMU stuff in rom_patches.cpp,
   but there are too many uncommented magic numbers there
   for me to understand what it is doing!




> Maybe it's enough poke a value != 0 there after MacOS has started.

	Poke? Looks like BASIC is gone, but not forgotten ;-)


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