*** C128 Auto-boot sector layout *** Document revision: 1.1 *** Last updated: March 11, 2004 *** Compiler/Editor: Peter Schepers *** Contributors/sources: unknown The C128 has the ability to auto-boot a floppy disk that is in the drive when the system is powered up, but only if track 1 sector 0 contains a specific signature. Below is a dump of an auto-boot sector with its signature. 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 0000: 43 42 4D 00 0C 00 02 00 00 A5 D7 C9 80 F0 03 20 CBMɀ 0010: 5F FF A9 05 8D 06 D5 A9 4E 8D 00 FF 4C 00 0C 00 _թNL 0020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0090: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00A0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00B0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00C0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00D0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00E0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00F0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Bytes 00-02: Auto-boot signature 'CBM' 03-04: ??? 05-06: ??? 07-08: ??? 09-1E: Boot code 1F-FF: ??? Below is a disassembly of the machine code contained from 09-1E. org = $0c00 lda $d7 cmp #$80 beq skip1 jsr $ff5f skip1 lda #$05 sta $d506 lda #$4e sta $ff00 jmp $0c00 .end The only document I have found which attempts to explain the layout of the C128 boot sector doesn't fit at all for the above sector layout. I am therefore not yet sure of all the details in the above sector. Anyone who has more info can contact me so I can update this document.