Date   : Thu, 11 Aug 2011 19:10:26 GMT
From   : jgh@... (J.G.Harston)
Subject: Risc PC (Was 'Minitel in France')

Rick Murray wrote:
> This seems to imply, to me, that a given memory location may exist in
> two different places - the physical address and the logical address. Or
> does the MEMC 'hide' physical locations from the processor?

Yes, the layout in the PRMs does seem to suggest that. It looks
like that if the CPU is in supervisor mode, then %0xxxx is logical
memory, %10xxx is physical memory, %110xx is I/O and %111xx is ROM
(with some I/O hidden underneath it). Accessing %0xxxx is
translated to an access to an appropriate part of %10xxx.

It also implies that there is more logical memory space than
physical memory space - huh? Logical memory occupies to
"superpages", &0x and &1x, but physical memory occupies one
superpage, &2x.

-- 
J.G.Harston - jgh@...      - mdfs.net/jgh
Whitby Yards Gazetteer - http://mdfs.net/Docs/Books/YofWhitby/Gazetteer