The Dallas Quest - Single ATR version

[Wrathchild]

Following up on the work in making the Dark Crystal run from a single ATR, I've gone and done the same with this title.

 

Some fun and games were had due to the copy protection revolving around XOR patterns dependent on the data previously decoded and so any attempt to modify a value would certainly mess everything up.

 

With Altirra's debugger it is simple enough to track and break execution after the decoding of a section has been completed. At that point I dumped the relevant areas of memory out to file, superimposed that back over their original place in the ATR and then tweaked the bits of code that would try to decode it during and after being loaded so that they don't affect memory, i.e. it just loads it cleanly.

 

The long shot of that is that 1) the game still loads and 2) the ATR image was then editable to include a few other tweaks:

 

a) thankfully, for the graphics & code specific to a 'location' that is loaded in, there is a sector map table used to load the data. By sticking the two disks together this meant that the offsets were easy to update.

b) the game's save positions are located at the end at side 2. Therefore a simple patch to the sector offset used means loading and saving work too.

c) When I checked the disks on AtariMania there seems to be no difference between the Datasoft and US.Gold releases and so the colours in the PAL version are a bit naff. I've hook a small piece of code (at $580) to patch up the 'colours-per-location' table to hopefully improve this (and a few other places where colours are set). These remain 'as-is' under NTSC.

 

Enjoy,

Mark

Dallas Quest, The (1984)(Datasoft)(US)(Combined v1).atr

[Mclaneinc]

Thanks Mark, great work as always..

 

Appreciated!

[ndary]

excellent work!!!

[Wrathchild]

Oh, I forgot to mention. The game has an odd method of checking the correct disk side is present.

The 8th Sector on Side 1 contains the word 'WRONG'.

When the check is asked for it succeeds if the text is not found, rather than checking for a pattern that does exist.

This means that you could put any other disk in than side 1 and the check will pass but of course the game will fail to load the intro and crash.

By putting the two sides in one ATR, the sector check has been inverted and so requires that a disk with 'WRONG' in sector 8 is present.

[+Philsan]

Thank you very much Mark.

 

I opened my letter "A" games folder and I found the attached ten Adventure International adventures (Hulk, Spider-Man, Voodoo Castle...) on two disks; perhaps they share the same disk side checking so you could fix ten games in one shot.

Adventure International.zip