> > > total memory = 103 MB
> > > hw.physmem = 108613632
> > >
> > > What happens to the other 428k?
> >
> > eaten by the monitor, maybe?
> 
> What monitor? The ROM based serial console monitor? While that's feasible,
> almost 1/2 a meg on a machine that ships with 8 megs is a LOT.
> 
> Any other ideas?
> 
No, it is correct. The firmware uses that memory. It's not accessible
for an operating system, and I don't know what it is used for.
The top of useable memory is reported via the RPB at boot.

-- Ragge