Resource centre for ZX Spectrum games
using Manic Miner and Jet Set Willy game engines
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Manic Miner & Jet Set Willy Yahoo! Group
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Message: 6418
Author: jgh@arcade.demon.co.uk
Date: 17/04/2008
Subject: Re: JSW48 toilet-run / item-count /
> Message-ID: <fu5tah+sflr@...>andrewbroad wrote:
> equin0x80 wrote:/Below/ 8000? Nowhere.
> > 3. Not sure whether I'll get anywhere with this, but I might try to=20
> > add a small interrupt routine coded by somebody else (probably 1 or
> > 2 KB which must not be overwritten). Where is it safe to add things
> > below 0x8000 without the game stomping on them?
4000-5B00 : Screen
5B00-5C00 : Stack
5C00-5E00 : Attribute buffer 1
5E00-6000 : Attribute buffer 2
6000-7000 : Screen buffer 1
7000-8000 : Screen buffer 2
You /might/ be able to squeeze something into page &5B as the
stack is unlikely to use all of it. A snapshot of JSW suggests no
more than four items are pushed on the stack, so &5B00-&5BEF
are likely to be safe, leaving space for eight stacked words.
Refering to http://mdfs.net/Software/JSW/Docs/CodeLayout you could
also try 869F-87C9 which contains the password entry code and
gives you 299 spare bytes. If you're looking for 2K of space
you'll be out of luck unless you sacrifice some rooms.
I'm also not sure how you'll get an interupt routine called with
the memory map so full, unless you mean a ticker routine called by
the main gameplay loop.
--
J.G.Harston - jgh@... - mdfs.net/User/JGH
A Review of Sheffield City Council's Members' Allowances Scheme
See http://mdfs.net/payreform
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