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Jsw Loader Differences

jsw loader

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#1 Spider


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Posted 15 August 2014 - 07:17 PM

There were four releases (five if you count the PGC bugfix) although with a few exceptions the loaders are about the same.

Loader: Pre-Production


Loader: Normal


Loader: PCG Bugfix:


Loader: Ventamatic


Loader: Re-Release "They Sold A Million"


Saver: Re-Release "They Sold A Million"


The Pre-Production / Normal / PCG Bugfix releases all share an identical loader. The Ventamatic release is very similar, apart from the obvious text change the only other difference really is the use of the bright attribute in the listing along with setting the paper yellow for the text.

The compilation Re-Release on "They Sold A  Million" uses Speedlock. The 'saver' routine is loaded and the game code is loaded at a lower memory point to allow the Speedlock saver to sit in upper memory.

This saved the whole lot from screen memory downwards. Unfortunately, the 'save' did not include the speedlock saver itself, the code terminates after 32768 bytes from 25000 ie 57768 and the 'Saver' builder lives right near the end during "build" at 65024. The saver code shown is what is present when the game is running. I have heard that a few games using Speedlock have saved the 'saver' code as well, once I have found one of these it will be interesting to examine as there is currently only the Alcatraz utils available and these are very dificult to use, I've yet to manage it.

The speedlock code is not really something I fully understand, the 'basic' is shown in the screenshot above however there is far more code present. Its protected using both odd line numbers (0 a few times) as well as attribute changes.

Changing order to chaos since 1984

#2 Spider


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Posted 17 December 2016 - 08:05 AM

There's also another variation too. The 'Normal' loader some variants have line 30 as LOAD "Jetset2" instead of 30 LOAD ""


The code block is completely identical however.

Changing order to chaos since 1984

#3 jetsetdanny


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Posted 17 December 2016 - 10:03 AM

It's a very interesting analysis, Andy - thanks!  :)

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