[B2-devel] Re: Any use of MMU emulation?

[Brian J. <bjj...@us...>]

Gwenole Beauchesne <gb...@di...> wrote:
> I was wondering if B2 would benefit from MMU emulation. Some users
> want it because:
>
> 1) It enables the use of virtual memory.
>
> My opinion is that if a user wants X MB of virtual Mac memory, where
> X > physical memory available to the host system, he can already do
> so.  The host system will handle much better extra memory than
> letting MacOS swapping to the hardfile.

Yes.

> 2) It enables other systems to run under B2.
>
> This is a false problem. B2 is "only" a Macintosh emulator and
> doesn't emulate much of a Mac hardware. So, if B2 were to have MMU
> emulation, Linux or other systems will probably not work anyway.

Certainly.

> Other ideas?

It may be useful as a development vehicle for PPC support, if PPC
MacOS is more dependent on the MMU.  But that's a long shot.

BTW, any thoughts on running MacOS X on a PPC BasiliskII?

> There are currently two MMU implementations available on top of
> UAE:
> ...

Would it be possible to do a hardware-assisted implementation?
I.e. have the Mac load directly from Mac virtual addresses (with an
appropriate direct-addressing offset), without translating them to
physical addresses, and use a segfault handler to catch TLB misses and
mmap() the corresponding "physical" page from a file?  We'd need some
way to handle different host and Mac page sizes....

						Brian

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