fred@cbmvax.UUCP (Fred Bowen) (10/01/87)
> All auto-start cartridges for the C64 contain 5 bytes of Auto-start code > starting at location $8004 (at least as I can remember). These 5 bytes are > checked by the computer at power-on. When you plug a C64 cartridge into > a C128, the 128 recognizes these bytes as being the 64 startup. The 128 > mode auto-start uses a slightly different sequence of characters to indicate > that they are 128 mode cartridges. Wrongo. As I posted earlier, the C128 at powerup is running in Z80 mode. The Z80 looks at the hardware lines to see if there is a cartridge there, or to see if yer finger is holding down the C= key. It does not address the cartridge and look for 'CBM80' out there- that is done by the 6510 processor long after it's already in C64 mode. The C128 cartridge has a different signature because it was more flexible- the card tells the Kernel when to call it- before or after (or both) initialization is complete, etc. It is similar to the Plus/4 routine- cartridges are 'logged in', allowing one card to see if another is there via its ID. -- -- Fred Bowen uucp: {ihnp4|rutgers|caip}!cbmvax!fred arpa: beats me tele: 215 431-9100 Commodore Electronics, Ltd., 1200 Wilson Drive, West Chester, PA, 19380