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krick
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Reged: 02/09/04
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Re: Patched Robotron 2084 by Christian Gingras
12/17/14 09:29 AM


This page mentions how the checksum bytes are calculated...

http://www.donhodges.com/how_high_can_you_get2.htm

Quote:


The checksum routines in this game first add up all the even bytes in a memory bank and check against #00, and then repeat this for the odd numbered bytes in the memory bank. We do some quick math and discover that the new programís even bytes add up to #18B less checksum bytes than the program it replaces, and the new programís odd bytes add up to #187 more checksum bytes than the program it replaces. To fool the programís checksum we therefore add #8B to an unused even memory location and #79 to an unused odd memory location.





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Entire thread
Subject Posted by Posted on
* Patched Robotron 2084 by Christian Gingras McHale 12/12/14 05:50 PM
. * Re: Patched Robotron 2084 by Christian Gingras RobbbertModerator  12/12/14 09:45 PM
. * Re: Patched Robotron 2084 by Christian Gingras krick  12/13/14 06:34 PM
. * Re: Patched Robotron 2084 by Christian Gingras RobbbertModerator  12/13/14 06:52 PM
. * Re: Patched Robotron 2084 by Christian Gingras krick  03/28/15 05:38 PM
. * Re: Patched Robotron 2084 by Christian Gingras Phantom DJ  05/01/15 09:49 AM
. * Re: Patched Robotron 2084 by Christian Gingras RobbbertModerator  04/04/15 12:37 AM
. * Re: Patched Robotron 2084 by Christian Gingras krick  12/14/14 01:15 AM
. * Re: Patched Robotron 2084 by Christian Gingras RobbbertModerator  12/14/14 02:30 AM
. * Re: Patched Robotron 2084 by Christian Gingras krick  12/15/14 07:35 AM
. * Re: Patched Robotron 2084 by Christian Gingras krick  12/17/14 09:29 AM

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