anybody dump their NTSC bios?

[RevEng]

I recently compiled the 7800 NTSC BIOS source code at Dan Borris' page, and discovered that it has 3 different bytes, compared to the "common" NTSC BIOS that's floating around the internet, and used by the emulators. One differing byte is just a modified "error code" used at $FFDD. The other two bytes that differ are the IRQ vector at $FFFE. Dan's disassembly points to $FAAA, which is actually an interrupt routine. The common BIOS points to $F933, which locks the console in 2600 mode.

 

This got me wondering about the possible BIOS revisions out there. If anybody has dumped their own NTSC BIOS and is willing to share, I'd love to see it, and compare it to the other two. Multiple submissions welcome.

[CPUWIZ]

Crap, I threw most of them away. Never occurred to me to keep them.

[+Mitch]

I have dumped several and the production ones were all the same. There was a bad dump of the 7800 BIOS that was floating around the net for years, a couple of wrong bytes at the end if I remember correctly. It is possible this disassembly was based on that one. Here's the bad dump if you want to compare. http://www.atari7800.org/bin/a7800/olda7800.zip

 

Mitch

[RevEng]

No worries, WIZ. All of this is pretty much academic.

 

Thanks for that bad bios, Mitch! The last 2 bytes in it match the ones from the disassembly, so I'm thinking you're right that the disassembly was based on it.

 

The disassembly does have a differing byte in the error code handler at $F8DD. (ldy #4, instead of ldy #2) I'm thinking this was introduced as a typo at some point, since it's between error code handlers #1 and #3.