Re: Where have all the buffers gone? (long time passing...)

[nathan@cco.caltech.edu (Nathan Mates)]

In article <4lo8v0$rem@tuba.cit.cornell.edu>,
Jay Krell <jmk3@crux4.cit.cornell.edu> wrote:
>bciu4@epix.net writes:

>I know almost nothing of ProDOS 8 and Basic.System, but
>I believe one common problem loading stuff with both
>or one of them is that there is some memory map, maintained
>on a page by page basis. If a page is marked used, you cannot
>load stuff to it. For example, I believe the text pages are
>marked used, so you can't bload a text or lores screen.

   This would happen to be for a darn good reason: there are screen
holes used by cards and everything else in addition to the text screen
in 0[01]0400-800. Indiscrimanently writing to them without a clue is
very stupid. [For example, the 80 column card stores its horizontal
cursor position in 1403 (decimal), which is in this area]

>Solutions include 1) mark the pages unused (not sure this
>is so kosher) or 2) load the data elsewhere then move it
>to where you want it.

   If you're going to move stuff around that area above, then copy 120
(=40 * 3) bytes to 0400, 0480, 0500, 0580, 0600, 0680, 0700 and 0780.
As I said above, writing to the text (== lores graphics) screen is
stupid and should not be done unless you know dang well what effect
this will have on all cards.

   [This post appeared as a followup without much of an antecedent,
and I couldn't tell from the context quoted by Jay to see if I'm
answering the original question. Apologies in advance if I'm going off
on an irrevelant tangent.]

Nathan Mates



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<*> Nathan Mates http://www.ugcs.caltech.edu/~nathan/      <*>
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