[CDG5] MemRetry's objective

Elliot Nunn elliotnunn at fastmail.com
Tue Apr 2 08:13:02 AWST 2019


Wow! It would be brilliant to have an accurate OldWorld Power Mac
emulator. Once I (finally) get Cube-E building, I hope to develop/RE a
minimal patch to get it running on RISC.

Slight twist (and apologies for being off topic): I just found that the
linked patches (lpch resources etc) hardly changed from System 7.1 to
Mac OS 8.1 (after which I think they disappeared). This is probably
explained by Apple using SuperMario, with its ROM vectorisation
mechanism, for all late-Quadra and Power Mac ROMs, and thus obsoleting
the linked patch mechanism. As they stand, then, the linked patches are
a powerful and modular instruction book for "modernising" or "System
7-ising" any Mac ROM as far back as the first "128K" Plus ROM. Neat!

> On 2 Apr 2019, at 7:51 am, Max Poliakovski <maximumspatium at googlemail.com> wrote:
> 
> Wow! I call it a "real quick" reply :)
> 
> Mainly misaligned accesses. An emulator might not complain about these, but I would expect MAME to be pretty accurate!
> 
> So PPC load/store instructions will cause DSI on misaligned access and memretry will magically fix that? That sounds cool :)
> I don't actually know how the emulated CPU in MAME handles misaligned accesses. Tomorrow I'll try to enforce it to see what happens...
>  
> Does MacOS for PowerPC boot in MAME?
> 
> Currently it doesn't because MAME's emulation is still incomplete. Two years ago, I sent them several patches fixing CPU emulation so their model of a PowerMac 6100 almost reaches the gray screen. A hardware emulation issue related to CUDA/NVRAM is currently preventing it from booting - it seems that external interrupts won't be routed as expected. That causes the Netboot driver to hang forever. I think I'll be actually able to fix it...
> 
> Cheers
> Max
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