BOOTING CP/M ON THE C128 FROM DEVICES 9, 10 OR 11 by Ismael Cordeiro (ismael@cam.org) As you should have already noticed, CP/M on the C128 only boots from device 8. I decided to find a way of making it boot from device 9 because I have a 1571 as device 8 and a 1581 as device 9 and when I boot CP/M many files are automatically copied to drive M. Booting from a 1581 saves me 25 seconds. With a 1541/1571 boot disk the only way to change the device CP/M boots from is by changing the CP/M boot routines in ROM and burning new EPROMs. However, with a 1581 boot disk you can easily make CP/M boot from devices 9, 10 or 11. Of course this only works with the 28 May 87 version of the C128 CP/M because it's the only one supporting the 1581. It also works with Simeon Cran's ZPM3 installed. Maybe it won't work with modified versions of the C128 CP/M, like BIOSR4, BIOSR6, etc., because of address changes but I haven't checked it. - Format a CP/M 3.5 DISK and copy CPM+.SYS and CCP.COM to it. - Using a CP/M disk editor (ZAP, EDFILE, FU, etc.) change the bytes below in CPM+.SYS. The addresses and sectors (or records) below assume that the file starts at address 000 and that the first sector (or record) is 0. If in your disk editor the file starts at address 100 and/or the first sector is 1 you'll have to add 100h to the addresses and/or 1 to the sector numbers. Address Sector Byte 0E6E 1C 01 (01=device 8, 02=device 9, 03=device 10, 04=device 11) 112F 22 00 (00=device 8, 01=device 9, 02=device 10, 03=device 11) Don't forget to write the changes to the disk! - Go to native mode and with a sector editor change the bytes below. Track Sector Position Byte 40 5 45 8 (device number: 8, 9, 10, 11) 40 8 117 8 (device number: 8, 9, 10, 11) To be sure that the byte is the right one, check the sequence 169 15 162 8 (A9 0F A2 08 in hexadecimal) on both sectors. The byte to be changed is the 8 at the end of the sequence. Don't forget to write the changes to the disk! - Put the disk on the device you chose and enter BOOTUx (x is the device number). I would like to thank Myklos Garamszeghy for his excellent articles in Transactor and Randy Winchester for clues that led me to the right path.