The format of the Boot command is now as follows:–
B Boot drive A, double density, sector 0, 5.25 inch
B sscd Where sscd is a single hexadecimal value.
Leading zeroes may be omitted.
ss is the physical sector number to be read. Normally this is 0 or l.
c is the command digit which has the following possible values:–
0 5.25 inch, double density
1 5.25 inch, single density
3 8 inch, single density
d is the drive select digit which has the following possible values:–
1 drive A
2 drive B
4 drive C
8 drive D
Examples of the enhanced Boot command
B 2 Sec 0, 5.25 inch, DD, drive B
B lll Sec 1, 5.25 inch, SD, drive A
B 134 Sec 1, 8 inch, SD, drive C
First make the patches to bring V2.0 to V2.1, if needed.
Address V2.0 V2.1
F068 30 31
F108 20 ED
F109 04 Al
FIOA ED 20
F10B 4l 02
Then make the patches to bring V2.1 to V2.3.
At F068 change 31 to 33
At FBO8 change 3A 60 00 to CD EF FF
At FCO3 change 11 99 FC to 3D 20 FD
At FC11 change 20 27 3E DO CD 8C FC 3E O1 D3 E4 36 5B
to 11 99 FC 20 24 3E DO CD 8C FC CD DE FF
At FC42 change AF D3 E2 to 00 00 00
At FFDE there are FF characters to the end – change these to
3A 61 00 B7 20 01 3C D3
E4 3A 62 00 D3 E2 3E 5B
c9 3A 60 00 B7 20 06 21
00 00 22 61 00 FE 02 DO
These changes have been carefully checked and the results fully tested,
so you should have no difficulty. You can check that you have typed in the
changes correctly by using the standard CRC calculating program. For your
convenience this program has been run separately on the first 2K of RP/M V2.3
(CRC = EF 24) and the second half (CRC = 58 CD). Therefore you can easily
confirm that your new RP/M 2.3 is correct. The CRC calculating program is
called CRC.COM and is the subject of another article in this issue.