Subject: Re: the prom: to map or not to map
To: None <netbsd-ports@NetBSD.ORG,>
From: Wolfgang Solfrank <>
List: netbsd-ports
Date: 06/11/1997 18:55:49
> > Now for why this isn't the prom: the firmware, upon startup, copies itself
> > from rom to ram (the speicification requires this, but note that OpenFirmware
> > on PowerMacs doesn't do it), relocates itself to the ram addresses, and
> > then runs from the ram image.
> Also very interesting. I guess it allocates its own stack too?

Hmm, since OpenFirmware is a Forth dialect, it doesn't have one stack, but
several.  This it allocates/manages itself.

> I see. I guess the alternative would be to only allow entry back to the
> firmware on shutdown where you would have to read it back in from rom as
> a shutdown hook or something. Certainly for .5 MB and the convenience of
> being able to pop into the firmware at any moment this makes the most
> sense. Interesting.

Hmm, there is no defined interface into the firmware residing in the rom.
So to be most portable we have to stick with the copy in ram.
ws@TooLs.DE     (Wolfgang Solfrank, TooLs GmbH) 	+49-228-985800