Re: [B2-devel] MMU stuff

[Christian B. <cb...@st...>]

Hi!

On Thu, May 17, 2001 at 11:00:55AM +1000, ni...@in... wrote:
>    (MacPerl's LowMem.pm, and LowMem.h from Apple's Universal Headers)
>    and it seems that 0x0CB2 is the address. 0x0CB1 appears unused

0xcb2 is a flag that indicates whether the MMU is in 24-bit or 32-bit mode.
The "mmu " Gestalt in the 1MB Mac ROMs looks at 0xcb1.

>    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.

This is actually the same flag as 0xcb1 (ROM system init sets the BootGlobs
flag and it gets later copied to 0xcb1), so 1=AMU, 2=reserved, 3=68851,
4=68030, etc. When this flag is <>0, the ROM/MacOS startup code will most
likely also access other information in the BootGlobs that isn't there
(MMU tables for 24/32 bit modes).

> > Maybe it's enough poke a value != 0 there after MacOS has started.
> 
> 	Poke? Looks like BASIC is gone, but not forgotten ;-)

C64 rulez! :-)

Bye,
Christian

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