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Madi

Modification of XL-(OS ROM) triggered Memory Test

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I tried do modify the 600XL-800XL (OS ROM) with a disk editor to make it compatible with MyDOS - Ultra-speed utility.

I modified the area CC00 - CE98 which is allocated for the International character set. I tested the modified ROM using Altirra.

I got the following bad ROM image and never pass it :) :

 

8ANo8S.jpg

 

Are the Atari's XL OS ROMS tested for a checksum identification upon run? or only for some parts/locations of the OS ?

Why does copying ROM to ram and then saving them back as ROM succeed although they may be altered ( e.g.The Translator)?

 

:?

 

madi

Edited by Madi

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As you discovered, the OS does a ROM checksum. You can disable the checksum by storing $EA into $C31D-$C31E.

 

Bob

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@ bob1200xl

 

@ David_P

 

Thank you for the clarification. I will "EA" those 2 bytes and continue with my hacking project .. :)

Edited by Madi

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