What does the 7800 bios do?

[yllawwally]

Does the 7800 bios do anything other than determine if a game is 7800 or 2600?

[EricBall]

IIRC it also does some sanity checks on the 6502 & other hardware along with the fuji graphic while it verifies the digital signature. There's even a disassembly with some comments: http://www.atariage.com/7800/archives/bios7800.asm

Edited March 13, 2013 by EricBall

[DanBoris]

IIRC it also does some sanity checks on the 6502 & other hardware along with the fuji graphic while it verifies the digital signature. There's even a disassembly with some comments: http://www.atariage....es/bios7800.asm

 

Yep, this is all it does. Once the verification is complete the bios is swapped out for the cartridge ROM so isn't even used after the game starts. So technically it's more of a boot loader then an actual bios.

[Blue Azure]

Hello to Eric & Dan & Wallyworld,

 

This is a full disassembly of the original 1984 release. I put the hex on it.

7800_NTSC_OLD_BIOS_DISASSY_E972.rtf

 

Can someone plug this 1984 binary into a 1986+ machine and tell me if it works? It seems like it should.

7800BIOS_old_E972.bin

 

THX, BLUE