On Wed, 26 Dec 2001, gabriel rosenkoetter wrote:

> On Wed, Dec 26, 2001 at 02:48:24PM -0800, Bill Studenmund wrote:
> > Hmmmm... I just had my machine open earlier today to add RAM, and I
> > thought that the PROM was on its own DIMM (different shape from the
> > SDRAM). Also, I thought someone had scavanged PROMs from other machines
> > (2.0 and 2.4), and had boot failures follow the 2.4 PROM regardles of
> > which MB it was in (there is a MB difference between the early and later
> > Beige G3s).
>
> I know the SIMM (pretty sure it's not a DIMM) slot you mean. It's
> empty on my (1.0.5) 7500. So the PROM is somewhere else on that
> motherboard, though they left themselves an upgrade path (which
> they never took?).

Oh, Apple has done that for a while. What it means is that all you'd need
to do (if it could be done) is stick in a new PROM

> > So the changability is there. ;-)
>
> Well, in theory. What are the chances of writing one's own firmware
> controller? Can we even get the necessary docs from Apple? (I know
> there are "open source" BIOSes for PCs...)
>
> > I don't think so. Certainly for the 1.0.5 machines, the CPU was different.
> > They might not have support for different CPUs in different OFs. Also,
> > part of our problem initially booting on the Blue & White G3s was they
> > used a different Host->PCI chip than the Beige ones, and we had to add
> > support.
>
> Sure, but all the OF needs to see is a PCI tree, and it should still
> know how to speak to all the correct stuff, shouldn't it?

I'm not sure. I bet it also needs to know how to configure the memory
controller. I'm not sure how that's done, and I know that the chipset has
changed with time. Coincidentally, the changes coincided with OF version
changes. :-)

> As far as the processor issue, if OF 1.0.5 is able to deal with any
> kind of PPC (including G3 and G4) in a processor slot, it'd be kind
> of silly if OF 3 couldn't deal with a 604 or 603...
>
> (I'm well aware that I'm speaking to what things reasonably should
> be here, and that reality might be drastically different, especially
> with a proprietary hardware vendor.)

:-)

Take care,

Bill