Re: A86: can one program be on two pages?

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Re: A86: can one program be on two pages?



On Wed, 24 Jun 1998 10:16:28 -0400 Bryan Rittmeyer <bryanr@flash.net>
writes:
>
>Hi,
>
>Once again I'm going to annoy you all with my lame newbie questions..
>but seeing as how the TI-86 uses a paged RAM (as well as ROM, of
>course) system, isn't it possible to have programs start on, say,
>page 2 and overflow into page 3? In theory I could load page 2
>into the low 16k and page 3 into the high 16k - that would
>accomodate programs up to 32k (in theory). Is there a ROM call to do
>this? If not, does the byte receive code in the ROM check after
>-every byte- to see if its overflowed the current RAM page and in
>that case swap in a new page? I know I can use _load_ram_ahl to
>automatically swap in the RAM page where a program begins... but
>what happens if the program is bigger than 16k? Is there a limit
>on the calc of 16k, 32k, or none at all? If programs can be more than
>32k (and I believe somebody said they can be up to 64k) then the
>calc has to do some checking in link routines as to whether or not
>it needs to swap onto a new page. This could potentially get very
>messy... I'd need some kind of routine to convert between an absolute
>address and a RAM page/hl combo (like _load_ram_ahl)

asm programs are limited to something like 9k or 12k or something.

well, i said before (kinda hidden):
unless you switched _load_ram_ahl with one of those deals that loads two
ram pages at once...  maybe: (might work, might not, anyone wanna test
it?)
     call _load_ram_ahl
     out ($05),a
     inc a
     out ($06),a
     res 7,h
     set 6,h

and end with
     out ($05),$0d

that would load two ram pages.  i think it should work, hl would point to
wherever just like if you called _load_ram_ahl.

also, _conv_ahl $4633 gives you the ram page #, add $40 and send it to
the port and you've got _load_ram_ahl.

>receive, but it seems awefully slow. Swapping RAM pages must take
>quite a few CPU cycles. Will _load_ram_ahl still swap pages if the
>right page is already swapped in?

it's quicker to just swap than to check.  it's calculating what page it
needs that takes time.

>could have spent another $2 and put a 68k into the damn thing...

but that's a more complicated processor...  i don't like complicated
things

-josh

>
>-- 
>Bryan Rittmeyer
>mailto:bryanr@flash.net
>http://www.bridges.edu/horizon/
>

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