> Date: Fri, 11 Dec 2020 17:24:51 +0100 > From: "Peter J. Philipp" <p...@centroid.eu> > > Hi, > > Now that POWER9 systems are pretty well supported, I'm setting away > some time next year to backport powerpc64 to the Mac G5. Is there > anyone already doing that? I already tried this once (based on the > macppc sources) but failed. I don't want to throw the little that I > learned out the window. I'm giving myself more time next year than > my last attempt. Right now I'm dreaming big, but I'll need to awake > to do some work on this. I'll likely start in January or February > with compiling on G5 macppc arch and testing on amd64 under qemu. > Please don't give me any kudos until I share something that > works. :-)
Hi Peter, The core powerpc64 kernel code (pmap, traps, etc.) should work just fine on the PowerPC 970. The powerpc64 <machine/endian.h> uses instructions that the G5 doesn't have, but that is trivial to fix. Your biggest challenge will be the firmware differences. The POWER9 machines use OPAL whereas the older systems use Open Firmware. The way I envisioned supporting Open Firmware systems is to have the bootloader translate the Open Firmware device tree into a "flattened" device tree before entering the kernel. That way you don't need a special kernel for the G5 systems. One warning though: we may switch the POWER9 systems to little-endian at some point in the future. Supporting both big-endian and little-endian in the codebose shouldn't be a huge burden. But I'm not sure we'll have the infrstructure to build both big-endian and little-endian releases and packages. Cheers, Mark
