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Re: (03b3542ac93c) hw/ppc/mac_newworld: Restrict RAM to 2 GiB

From: BALATON Zoltan
Subject: Re: (03b3542ac93c) hw/ppc/mac_newworld: Restrict RAM to 2 GiB
Date: Thu, 1 Jul 2021 14:18:45 +0200 (CEST)


I've seen this commit 03b3542ac93c and remembered that mac99 has a strange behaviour that depending on options and if it's in qemu-system-ppc or qemu-system-ppc64 it behaves differently and emulates either

- a non-existing Mac config somewhat like a PowerBook (-ppc -M mac99)
- mostly a PowerMac3,1 (-ppc -M mac99,via=pmu)
- or some G5 Mac which is very unfinished yet (-ppc64 -M mac99)

For the first two 32bit configs limiting memory for 2GB is probably the right thing to do but a G5 Mac I think could have more RAM but not sure where it puts it on real hardware. This is probably not a big problem as G5 Mac emulation is not very good but I could at least run Linux on it so it somewhat works. Not sure if anybody wants to use it with more than 2GB RAM but this change now does not allow that (maybe it did not work anyway). I don't know if any action is needed just brought this potential problem to your attention. Do what you like with it.

I was also thinking it might be a good idea to break up the mac99 machine into multiple machines to avoid the confusing behaviour above and make it work more like other machines. This might also be good because qemu-system-ppc64 also includes all 32 bit machines as well so that way we could get rid of qemu-system-ppc or qemu-system-ppc64 and have only one command for all machines and users wouldn't have to know what options to use with mac99 to get a G4 or G5 Mac (I think qemu-system-ppc64 -M mac99,via=pmu -cpu G4 still works but it's not very intuitive -M powermac3_1 would be much clearer). I might give that a try but only if Mark would accept such patches otherwise it's just wasted effort to make changes to mac_newworld.c.

One thing I'm not sure about is at least that target_ulong is different on qemu-system-ppc and qemu-system-ppc64 and if that could cause a problem with 32 bit machines. But they are available in ppc64 now and appear to works but I was always using qemu-system-ppc so I haven't tested the ppc64 versions of these machines so there could be some corner cases I don't know about.


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