rb@mtuxn.UUCP (R.BOTWIN) (02/25/86)
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In response to numerous requests, I am posting some info on drive density
switching:
To change density, you must call SIO, after setting up the IOCB as follows:
Device=$31 (D)
Unit= Drive #
Command= $4E (N) to READ CONFIG
= $4F (O) to WRITE CONFIG
Byte Count = 12
Aux Bytes= (not normally used, but some DOS's use as part of formatting)
Also a "P" command is supported by some drives (like INDUS) to reconfigure
on demand prior to formatting.
The bytes transferred are:
byte 0: Tracks per side (40 std)
1: Drive step rate (west. dig. std....0 fast 3 slow)
2: zero (hi-byte of sectors/trk)
3: sectors per track (18 for std...26 for 1050 mode)
4: number of sides (0=single 1=double)
5: disk type:
bit 2: (0=single den, 1=double den)
bit 1: (0=5-1/4" 1=8 ")
6: hi-byte bytes/sector (0 for 810 compat)
7: lo-byte bytes/sector (128 for 810 256 for double den std)
8: translation byte:
bit 7: (1=40 trk on 80 trk drive)
bit 6: always 1 ...indicates drive present
bit 1: 1= make boot sectors (1-3) full size
bit 0: 1=sectors numbered 0-17 not 1-18
9-11: undefined
These bytes are transferred TO the progran on a read config, modifications
may be made, and a WRITE CONFIG will change the desired options.
The comment about it not working on an 810 is specious....Obviously
these commands will only work on configurable drives...like PERCOM, INDUS,
ATR8000 controller, etc.
On more note; thos using MYDOS are prompted for these options when using
menu selection P from DOS...It internally generates the CONFIG command
and executes it. I have placed a BASIC program to configure drives on
some ATARI bulletin boards, but I'd have to look for a copy now...
It's been several years since I wrote it!
Rob Botwin, N2FC
.....{utah-cs|seismo|decvax}!harpo!eagle!houxm!mtuxo!mtuxn!rb
ATT/IS Labs (201) 577-5016 (Cornet 8-270-5016)
FJ 1B-130njd@laidbak.UUCP (Nicholas J. DiMasi Jr.) (02/26/86)
I would like to add that MYDOS is not the only DOS that provides a command to configure (incl. switch density) such disk drives. DOS XL (from OSS) provides a CONFIG command that lets you specify single or double density and single or double sided for each drive. (My Percom drives will change density, but are only single sided, so I can't vouch for the usefulness of the single/double-sided switching.) Nick DiMasi Lachman Associates, Inc.