Re: Dualboot Mac OS X and NetBSD on Power Mac?

[Michael <macallan%NetBSD.org@localhost>]

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Hello,

On Apr 27, 2010, at 8:38 PM, Nathan Whitehorn wrote:

> On 04/27/10 19:21, Michael wrote:
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> > Hello,
> >
> > On Apr 27, 2010, at 6:01 PM, Dennis Ferguson wrote:
> >
> > > On 27 Apr 2010, at 13:10 , Chris Ross wrote:
> > >
> > > > On Apr 27, 2010, at 15:27, Michael wrote:
> > > > > On Apr 27, 2010, at 2:58 PM, Chris Ross wrote:
> > > > > > I have a quad-core Power Mac G5 that I'm thinking about pushing  
> > > > > > into a server-class machine in the closet at some point over  
> > > > > > the next year.  But, for now, it's still my primary desktop  
> > > > > > machine.  So, I have two main questions:
> > > > > >
> > > > > > 1) Does NetBSD/macppc run (well?) on this hardware?
> > > > >
> > > > > No.
> > > >
> > > > Okay.  Well, then that's clearly more important to address  
> > > > first.  :-)
> > > >
> > > > What doesn't work well?  Does it work at all?
> > >
> > > It worked at one point but the code seems to be bit-rotted; I had to
> > > fix problems in two files just to get a G5 kernel to compile.  I  
> > > managed to
> > > get to an ofwboot prompt, but it kept complaining about an  
> > > (unspecified)
> > > I/O error trying to read the kernel off the HFS disk.  I left it  
> > > at that
> > > point; I'll next try to boot it diskless when I have some time to  
> > > spend
> > > on it.
> >
> > Actually it gets much further - it hangs when enabling the MMU and  
> > so far I couldn't figure out why. Also, there's conflicting  
> > information out there about BATs being emulated in bridge mode  
> > ( most docs say nothing or no yet OpenBSD happily uses them anyway )
> > Also, there is no support for the PCIe bridge in last generation G5s.
>
> On the 970, all BAT instructions are no-ops. You can run them  
> without triggering a program exception, but they don't do anything.

Ah, ok. As it is macppc relies on BAT mapping PCI space 1:1.

> > > A 32 bit kernel, however, seems like it shouldn't be that  
> > > difficult.  This
> > > did work at one point, the only problem is that point was about 5  
> > > years ago
> > > and the rest of the kernel has moved on while that code has  
> > > apparently sat
> > > still.  It needs someone to work through its problems to revive it.
> >
> > Apparently it didn't really use bridge mode anyway - just ran a  
> > 64bit kernel being really, really careful about staying within 4GB.
>
> Also, the way Apple maps memory, the actual 32-bit cap is at 2 GB.

Well, I meant 4GB address space.

> > > > Is there any work being done on getting this hardware [fully]  
> > > > supported in the macppc NetBSD port?
> > >
> > > I don't think anyone could be running this code at all (in a  
> > > recent kernel)
> > > since if they were I'd expect not to get compilation errors when  
> > > trying
> > > to build a -current kernel.  I don't know about missing hardware  
> > > support
> > > (I can't see any indication that the G5's disk controller is  
> > > missing support,
> > > for what that's worth), but its current problems are more  
> > > fundamental than
> > > that in any case.
> >
> > You can compile a 32bit G5 kernel ( or at lease I could not too  
> > long ago ) - they don't reach userland however. 'Real' 64bit kernel  
> > hit an #error elsewhere, somewhere in OF support IIRC. Otherwise,  
> > we have a more or less generic SATA driver, no clue if that's  
> > enough for the G5.
>
> When I was doing the FreeBSD port to these, I ran into two issues  
> with SATA, which is otherwise a generic Serverworks/Broadcom SATA  
> chip. First, you need to issue a 4-byte read to the ATA status word  
> to actually have it updated, and second, you need to make sure the  
> interrupt is edge triggered, not level triggered, or you end up with  
> an interrupt storm.

Eww, I though PCI devices used level triggered interrupts by definition.
Otherwise, it's one bit flipped in OpenPIC.

have fun
Michael

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