Re: RFC : SOME IDEAS FOR THE APPLE II FPGA'ers

[bieling@terra.es (Jorge Chamorro Bieling)]

Michael J. Mahon <mjmahon@aol.com> wrote:

> 
> > 
> > Yes, every access to I/O space puts the whole thing into a slow cycle.
> > You don't need to think any further than $c000, which is being called
> > all the time. That's a big bottleneck. But this particular one can be
> > fooled by some kind of intermediate "buffer", latch or something. The
> > idea is to sowehow reduce the number of *real* accesses to MLB's $c000,
> > done in a way that is transparent to the software. After all, why would
> > you want to read the keyboard at a 1 Mhz rate (the Apple II bus limit) ?
> 
> But my point is, who cares how fast the processor is idling waiting
> for a keystroke--it's *idling*!

It maybe idling and then it won't matter, but it will more likely be in
the middle of a program that polls routinely the keyboard looking for a
certain keypress (a running Applesoft program polling for ctrl-C/ctrl-S,
or ESC, or whatever). You'd like the program to run as-fast-as-possible
but it just doesn't because the design overlooked this...

Unless there's a good reason to poll the keyboard so often, something
has to be done about the fact that it will be polled *too often*, the
end result being an innecesary, undesirable and very noticeable
slowdown.
-- 
Jorge Chamorro Bieling