Subject: Re: [stella] Misc 7800 From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx> Date: Wed, 19 Jan 2000 20:25:11 +0100 |
>> And why would these have back doors if they're Atari games? > >For various reasons.... :-) > >The main one being that the 2 main vectors (reset & NMI) jump >to code outside the keyed area (intentionally or unintentionally, >they didn't care). As mentioned, various games do this. Harry's >Monitor cart does this too. Minor mistake here. The reset vector has to point into the keyed area or it wouldn't pass the encryption check. A game would have to jump out of the keyed area after the encryption check started the code in there. Some games with bankwitching did that because they couldn't include the BS area in the keycheck, but still wanted to put some code there. Most games mentioned in the other post did the jump fully on purpose as the very first instruction. >Maybe a programmer got tired of waiting on the key process, >so they froze the keyed area. Of course this probably wasn't >the case since the devkit didn't require a keyed cart. Or maybe it was too much trouble to have the game keyed again and again during beta testing. They probably didn't have a dev system or a modified 7800 for all of their testers. The three games that the original question was about seem to be programmed by GCC for Atari, BTW. Thanks, Eckhard Stolberg -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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