Subject: Re: SV: Re: MPC860 or the mpc850de
To: None <>
From: Wolfgang Solfrank <>
List: tech-embed
Date: 02/21/2000 20:33:56

Let me start by telling you that last year I did a port of NetBSD to
a 403GCX based platform.  The 403GCX is an embedded PowerPC from IBM.
It has some similarities to the 860, especially it also has a software
reloaded tlb, albeit the organization of the tlb is somewhat different.

I do have the rights to and will release the source to the port after
some cleanup (and after some additional tuning which I'm currently doing).
Unfortunately, this will take some time.  However, there probably is
quite a bit of code there that could be taken for an 860 based machine.

> > We don't now what typ of memory model the mac use, like Big-endian ocg 
> > PPC-endian or Little-endian.

(What do you mean by PPC-endian?)  AFAIK, the mac uses big-endian. (Well,
it should be possible to implement an OS which would use little-endian,
but who in his right mind would want to? :-))

> I have studied the data books on the MPC821/860.  The memory management
> hardware is simpler than the 600 series, but Motorola made an effort to make
> it compatible.

Hmm, AFAICT the 860 mmu is quite different from the 6xx/7xx ones.
But since the tlb is software reloaded, you could ignore the hardware
support for hierarchical page tables and implement a page table scheme
more or less as you like.

> I think that the ofppc port may be simpler, thus requiring less
> modification.  I could be wrong here.

Hmm, you are right in that the ofppc port is simpler in terms of
hardware support, as it doesn't itself support any hardware directly,
but relies on OpenFirmware for that.  Therefor it might be easier
to single out the drivers from the rest of the code.

Depending on your periperals, and if you can wait some weeks, you
should probably better start with the ns3c port that should become
available then.


PS: I still CC'ed all the people on the original CC list, as I don't
know who's on tech-embed (albeit I suspect all of you are).
ws@TooLs.DE     (Wolfgang Solfrank, TooLs GmbH) 	+49-228-985800