On Tue, 28 Jan 1997 09:07:48 +0900 
 Masami and Ken Nakata <masami@fa2.so-net.or.jp> wrote:

 > Last time this line of topic was brought on the port-mac68k list, I
 > kind of got the impression from Joson (Thorpe)'s post that
 > NetBSD/powerpc ran on PowerPC systems with OpenFirmware support which
 > PCI-PowerMacs do have thus it was possible to run NetBSD/powerpc on a
 > PCI-PowerMac (not on the NuBus-PowerMacs that are supported by
 > MkLinux).  I deduced, because device drivers would have to interpret
 > OFW ROM each time it does I/O, it would run with some (probably
 > significant) performance penalty.
 > 
 > Would anyone care to clarify?

Well, I'm told that it doens't _quite_ run on PCI Powermacs just
yet (some minor tweaking to resolve some bootstrap issues, I guess),
but "almost".

In any case, you're correct in assuming that using OFW for i/o pays
a performance penalty.

However, the implementation of native drivers should be a mostly
SMOP, given appropriate documentation (or sample code).  In order to
support PCI and ISA on systems like Firepowers and Powermacs, only
a small bit of glue code is needed[*].  The rest of the PCI code comes
for free, since it's machine-independent.

[*] This is not strictly true, just yet.  NetBSD/powerpc, since it's
still fairly young, lacks the autoconfiguration infrastructure needed
to deal with differing PCI -> Host chipsets.  I'm currently working
on code to deal with the PCI -> Host chipsets on the Firepower computers,
and my design (which borrows heavily from NetBSD/alpha's autoconfiguration
model) will allow other PCI -> Host chipsets to be added very easily.

I'm still working out some of the details, and I hope to have something
interesting to post about here, sometime soon.

(FYI, the design I'm working on would also allow non-OFW systems to
be supported by a single kernel.)

Jason R. Thorpe                                       thorpej@nas.nasa.gov
NASA Ames Research Center                               Home: 408.866.1912
NAS: M/S 258-6                                          Work: 415.604.0935
Moffett Field, CA 94035                                Pager: 415.428.6939