Illegal jumps into the OS.
Posted: Mon Jan 10, 2005 3:04 pm
Just noticed that the recently added 'Q*Bert' game will run with OS-B only and I believe this is due to so-called illegal jumps into the OS.
I remember coming across a few games like this (an Asteroids clone and Pogo Joe spring to mind) which were easily fixed to run fine on XL machines by simply changing all the old JSR's into the OS with their new XL positions. This was easily done if you had a copy of 'Mapping the Atari (revised edition)'. Of course the games wouldn't run on the old 400/800 machines anymore but I wasn't aware of anyone who owned one of these anyway. I suppose it'd be possible to have a little sub-routine you jumped to which could check the machine you had and JSR accordingly (the menu created by Rob.C Menu Maker does something like this) but that seems too much like hard work!
Anyway, my point it that someone with a decent disk sector editor (Bob's Sector Editor was my favourite) and 'Mapping the Atari RE' could create an XL version of this game in a short amount of time! My copy of the book is in the loft!
I remember coming across a few games like this (an Asteroids clone and Pogo Joe spring to mind) which were easily fixed to run fine on XL machines by simply changing all the old JSR's into the OS with their new XL positions. This was easily done if you had a copy of 'Mapping the Atari (revised edition)'. Of course the games wouldn't run on the old 400/800 machines anymore but I wasn't aware of anyone who owned one of these anyway. I suppose it'd be possible to have a little sub-routine you jumped to which could check the machine you had and JSR accordingly (the menu created by Rob.C Menu Maker does something like this) but that seems too much like hard work!
Anyway, my point it that someone with a decent disk sector editor (Bob's Sector Editor was my favourite) and 'Mapping the Atari RE' could create an XL version of this game in a short amount of time! My copy of the book is in the loft!