Thread: Noob Questions
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Old 18 January 2006, 03:09   #2
Codetapper
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Join Date: May 2001
Location: Auckland / New Zealand
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1. Yes you have to search it in 2 blocks. It is best to disable fast memory and let the game load, then you can guarantee it is in chip memory and only one block to search! (Note that some games will override you and load into fast memory anyway as they detect it by poking values and seeing if they read back the same).

SysInfo is lying, your chip memory starts at $0 and goes to $1fffff. The first $c0 bytes are vital to keep the computer running but you can safely use memory from $c0 to $1000 despite what SysInfo tells you! Many trainer makers use low memory to store their keyboard cheat code to toggle infinite lives etc.

2. There are a couple of things you can do to get around this, a common trick is to replace the first file with a simple loader. Say the original game was "hunter", you write a program "boot" which loads "hunter", waits for the mouse (and at this point you can break into it with AR etc) and then executes it.

To load the file you need to open dos.library and LoadSeg the file, which loads it somewhere in memory. You will be given back the loading address of the file.

With a completely clean operating system you should find the same file will load to the same address each time. It's only if you soft-reboot with Ctrl-Amiga-Amiga that it will appear all over the place.

If you are using WinUAE you can use the debugger to cause it to halt when the code is in memory rather than in ROM. Create a config with only chip memory, let the program start to load, Shift-F12 to enter debug mode, "f", then and as soon as it finishes the debugger will appear and you can see where the code is.
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