Re: proposal: millicode

[Ignatios Souvatzis <is%netbsd.org@localhost>]

On Sat, Jan 19, 2008 at 08:37:18AM -0700, Tim Rightnour wrote:
> 
> On 19-Jan-2008 Frank Wille wrote:
> > Are there already known fixed offsets, which are used by other operating
> > systems, or do we choose them as we like?
> 
> Yes, AIX uses 0x3000 for the common code, and I think they implement locks
> around 0x4000, but I'm not sure about that one.  Aside from those, the rest we
> just choose as we like.
> 
> My thought was that we can set aside some pages between 0x3000 and 0x100000
> (ie, the start address for most OEA ports) and use those.  I'm thinking 4-8 or
> so 4k pages to start.  (This is also why I would like to see the rest of the
> OEA ports move to a common start address.  I think currently only sandpoint 
> has
> an odd one of 0x90000)
> 
> > And please keep in mind that there may be powerpc-ports which cannot
> > operate in low-exception-vector mode (MSR bit 25), like amigappc.
> 
> It shouldn't matter, as these aren't real exceptions that are called by the
> cpu.  However, I am curious as to exactly why the amiga can't operate in that
> mode.

Because at that address there is only Slooooooooooow RAM.  You don't want to
use it for anything else but DMA buffers for the audio device, the built-in
graphics, and the built-in floppy, that are connected to it.

        -is
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