Author: Ron (65-255-84-106.dyn.hsi.pldi.net)
Date: 11-16-2008 01:52
location 1802 ($70A) is DRVBYT.
It's a bit map for available drives in the system; default is 3 for drives 1 & 2 write buffers configured. Each bit in the low nybble enables a specific drive #:
0001 is drv 1
0010 is drv 2
0100 is drv 3, binary value 4
1000 is drv 4, binary value 8
0011 is 1 & 2, binary value 3
0111 is 1, 2 & 3 binary value 7
Other combinations are possible and emulators or special hardware could set any bit for drive numbers above 4. Be aware that more buffers take memory and raise MEMLO.
You must boot DOS into BASIC or ASMED to alter it and then write DOS.SYS and reboot with this disk to use it reconfigured. Alternatively you could also find the byte in the first sector of DOS.SYS with a disk sector editor, reset it and boot from that altered disk.
Mapping ATARI is online at the Antic project where you can read more.
HTH
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