Re: Clarification (was: Re: A82: PROPOSAL: TI-82 "Enhancement" Project)
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Re: Clarification (was: Re: A82: PROPOSAL: TI-82 "Enhancement" Project)
ADAMMAN106@aol.com wrote:
>
> In a message dated 98-02-23 19:25:54 EST, you write:
>
> <snip>
>
> > > Nathan suggested that the ROM was rewritten from scratch. I believe that
> > > is not possible, unless you only plan to include a few functions.
> >
> > Hmmm, why not? We've got the info for interfacing with most of the
> > hardware, it seems, so that's not a problem.
>
> I think what he means is that it wouldn't be feasible because of memory
> limitations on the calc, impossible to test, etc, blah, blah
Hmmm, well memory limitations are one problem, but impossible to test?
Why? Why can't we use an emulator or something (one is on the way, I
understand)?
> The Z80 can only address 64K of memory, and the calc allocates 32K for the ROM
> and 32K for the RAM
Yeah, I just found out about the 64K limit the other day while perusing
through the Calc-TI web archives. A shame. :-( But, still, the 86 has
got > 64K user memory availible, accomplished through memory paging
(which slows things down a tad, but still...). And I'm not sure, but if
we were to try and use that same technique to squeeze more than 64K into
the 82, it would most likely require hardware modifications that we
would not be able to make. Right? Could someone please explain memory
paging a bit? I KNOW what it is, essentially, but is it implemented via
software ONLY, or would the calc need more modifications to its hardware
than just a bigger RAM chip? If changes to the hardware are needed, are
they _big_ changes that we'd probably not be able to make?
TTFN,
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