[Gllug] The BBC and Microsoft.
jim
jim at madeira.physiol.ucl.ac.uk
Wed Oct 31 13:22:36 UTC 2001
On Mon, 29 Oct 2001, Steve Goodwin wrote:
> You'd have to store the PC for each task, then copy the instruction and
> execute it (unless it's a jump, in which case you'd emulate it), push
> all the registers & stack pointers back to your own memory area and then
> task switch!
Lord preserve us. The Beeb does have a timer IRQ! Task switching would
still be a pain though as no MMU means only one processor stack, so you'd
have to copy at least part of it each time.
> (there'd also be no supervisor mode on the chip, or memory manager
> making security a problem).
"Problem" is putting it mildly. "Non-existent" is more likely. Though some
of the RAM add-ons let you write-protect their memory, I think.
> Finally, a humanistic point: since there's no network (as standard) on
> either machine, you'd need a much larger keyboard :)
Serial port. User port. 1MHz bus. TUBE.
jim
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