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Date:      Tue, 23 May 2006 02:15:41 -0400
From:      Craig St Jean <valiantsoul@earthlink.net>
To:        freebsd-ppc@freebsd.org
Subject:   I may be able to help with getting it on a G5
Message-ID:  <6CB0FC67-E5DD-4C9C-9E00-4ACC32C30165@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 :)
I do have a G4 iBook which will help in the process until it boots on  
the G5. I'm not quite sure how to get everything over to the G5  
though - the only OS dev I've done was when the system was already  
running and I just made modifications.
>
> > 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.
Note quite sure how to do any of that but I will try looking into it  
once I get FreeBSD up on my iBook (going through things to make sure  
I get everything backed up - should have it up tomorrow or the day  
after. My work takes up a lot of time but I will do my best.



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