Resource centre for ZX Spectrum games
using Manic Miner and Jet Set Willy game engines
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Message: 6806
Author: john_elliott_uk
Date: 15/03/2015
Subject: Re: Question about inserting patch vectors in JSW64
If you're doing it in JSWED, you start by working out the address of the room. In JSW64:V games where each room is 512 bytes, that means room 0 is at 1:#C000, room 1 is at 1:#C200, room 2 is at 1:#C400 and so on.
Take the hex editor to that address plus #FB (so #C0FB, #C2FB etc.) You will see the two bytes #9F #86. This means the patch vector is currently pointing at #869F. If you look at that address, you will see #C9 (RET).
To change the patch vector, go back to the entry in the room (1:#C0FB, 1:#C2FB etc.) To change to #8149, replace the two bytes with #49 #81. To change to #8630, replace the bytes with #30 #86.
It's the same for variant X, except that the rooms are 1024 bytes. So the vector for room 0 is still at 1:#C0FB, but room 1 is at 1:#C4FB, room 2 at 1:#C8FB and so on.
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