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Meteor Storm (Compute! Issue 29) - Fixed for XL/XE

XL XE game fix Basic Magazine Type-in Compute

3 replies to this topic

#1 NuY OFFLINE  

NuY

    Chopper Commander

  • 226 posts

Posted Tue Aug 13, 2013 6:54 AM

I've been messing around with magazine type-in games again these last few weeks, at the minute I'm on Compute!.

I came across Meteor Storm and couldn't get it working under XE OS. Tried all sorts but it wasn't happening. MC was the only way, but my MC-fu is weak. Several hours later and I've found a memory move routine that works backwards (necessary in this case). Several more hours later and I've got it working after figuring out how to do addition in MC (very painful). A couple more hours and I've integrated it into the game and it is working fine, to my eternal joy.

Fix notes:
This game refuses to work on XL/XE systems as originally printed. The reverse
scroll of the meteors is achieved by fooling the OS into thinking it is in mode
0 when it is actually in mode 1, and then printing an insert line character at
the top of the screen. While this works on the 400/800 OS, under the XL/XE it
does something evil to the display RAM, corrupting it and making the game
unplayable.

To fix this, I have added a small MC routine to replace the print of the insert
line character. The MC routine detects the address of the start of screen RAM,
and copies lines 23-3 to the next line down in reverse order. A normal memory
move wouldn't have worked as the source and destination overlap.

And here they are; bootable ATR (Basic required), and the BAS and LST (as a TXT) files for your pleasure. Enjoy!

PS, Atarimania are more than welcome to add this to their database as a fixed version.

Attached Files


Edited by NuY, Tue Aug 13, 2013 7:43 AM.


#2 Grevle OFFLINE  

Grevle

    Moonsweeper

  • 383 posts
  • Location:Norway

Posted Fri Aug 16, 2013 4:29 PM

Thank you, The game is fun to play. :)

#3 feather OFFLINE  

feather

    Star Raider

  • 66 posts
  • Location:European Union

Posted Tue Aug 27, 2013 4:58 PM

Thanks!

Screenshots: http://atarionline.p...page=5#Item_20

#4 RodLightning OFFLINE  

RodLightning

    Dragonstomper

  • 773 posts
  • Location:USA Southeast

Posted Tue Aug 27, 2013 5:15 PM

Very cool.  It's never too late to add a new universally compatible game to the 8-bit library.  I was a Compute! subscriber for many years and sometimes typed in the listed programs.  This is exactly the kind of obscure stuff I like !!!  Thanks.  :thumbsup:

 

 







Also tagged with one or more of these keywords: XL, XE, game, fix, Basic, Magazine, Type-in, Compute

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