80-Bus News - November–December 1984, Volume 3, Issue 6

The format of the Boot command is now as follows:–

B		Boot drive A, double density, sector 0, 5.25 inch
		or
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 1.
	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 111	Sec 1, 5.25 inch, SD, drive A
B 134	Sec 1, 8 inch, SD, drive C

PATCHES REQUIRED

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	A1
FI0A	ED	20
F10B	41	02

Then make the patches to bring V2.1 to V2.3.

At F068 change	31 to 33
At FB08 change	3A 60 00 to CD EF FF
At FC03 change	11 99 FC to 3D 20 FD
At FC11 change	20 27 3E D0 CD 8C FC 3E 01 D3 E4 36 5B
to	11 99 FC 20 24 3E D0 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 D0
	AF C9

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.