[Gllug] The BBC and Microsoft.

[jim]

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
-- 
http://madeira.physiol.ucl.ac.uk/people/jim/
"... I naturally gravitated to London, that great cesspool into which all the
 loungers and idlers of the Empire are irresistibly drained."
                                - Sir Arthur Conan Doyle, "A Study in Scarlet"


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