On May 17, 13:06, Vintage Computer GAWD! wrote:
> On Wed, 17 May 2000, Pete Turnbull wrote:
>
> > Yes, probably :-) Since you wouldn't need much code, and nothing on a
> > standard Apple uses interrupts, you could go one further and make it a
> > time-sliced system instead of a cooperative one, with a very simple
circuit
> > (not much more than a 555 timer, though you might want it on a card
with a
> > PROM to hold the code).
>
> I considered this. An easier way to do this is to copy the BASIC ROM
into
> RAM in the upper 16K bank of memory and then modify the interpreter to
> switch after the execution of each BASIC program line.
Depends on whether you prefer hardware to software, I guess :-) Modifying
BASIC in a language card also has the advantage that it only tries to
switch when it's actually executing BASIC (rather than some DOS routine or
something you've BRUN) but I suspect that after-every-line is too often --
you'd spend a lot of time (proportionately speaking) context switching.
And it would be irregular; a multi-statement line encompassing a loop will
take much longer than a simple statement.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
Received on Wed May 17 2000 - 19:04:10 BST