Date: Sun, 21 May 2006 23:59:20 -0700 From: Peter Grehan <grehan@freebsd.org> To: Craig St Jean <valiantsoul@earthlink.net> Cc: freebsd-ppc@freebsd.org Subject: Re: I may be able to help with getting it on a G5 Message-ID: <44716148.6060801@freebsd.org> In-Reply-To: <B9B1DC30-FB6F-4573-9933-0B43296B7EC9@earthlink.net> References: <B9B1DC30-FB6F-4573-9933-0B43296B7EC9@earthlink.net>
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Hi Craig,
> Not sure if anyone has tried working on getting FreeBSD on a G5
> machine, but I have some free time and would be happy to help test. I
> have a quad 2.5GHz G5 PowerMac with plenty of memory and hard drive space.
Great ! I'm still struggling to resurrect my PPC dev machines and
environment, but when I do I'd like to get G5 support going. I'll take
any and all offers of help :)
> If someone gives me some direction on what may need to be
> done, I would be happy to try to help make FreeBSD run on a G5 system -
It's going to be tough. My plan is to get it running in 32-bit mode,
since full 64-bit support requires a massive amount of work, essentially
a new port.
What's there:
- the loader
What's not there:
- pmap support. The G5 uses 64-bit addresses in it's PTE format, so
it's just different enough than the G3/G4 to be annoying. The code is
already there to abstract out the differences, but a lot of
implementation work has to be done.
- the low-level assembler trap code needs to switch back to 32-bits.
This isn't too difficult, and the plan was to conditionally compile the
.S files similar to how ELF 32- and 64-bit support is done.
- no BAT registers, so the kernel needs to have virtual mappings
created for it. This complicates pmap startup, and various other parts
of the the machine-dependent code that assumes a 1:1 static mapping for
all memory (e.g. UMA_MD_SMALL_ALLOC, the syscons frame-buffer code, page
zeroing)
- cachelines are 128 bytes on the G5 as opposed to 32 bits on G3/G4.
This is almost abstracted out but some extra work is required.
- probably a bunch of other things I've forgotten.
> Unless everyone feels its not worth the time...
Definitely worth the time.
later,
Peter.
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