nep.pgelhausen@AMES-VMSB.ARPA (02/19/86)
In a reply to a recent query about disk densities, Rob Botwin said that the PERCOM density command format was copied by everyone including Atari. Sorry to say, from what I understand, Atari is the ONLY company making disk drives for the Atari which does NOT follow this standard. This is definately true for the 810. I cannot vouch for the 1050, but as far as I know it also is 'dumb' as far as density settings. It can read single density format disks, but unless upgraded, it cannot read or write true double density. Nor can you use the PERCOM commands to ask it it's current density or reset it. I assume that the "read the first sector" method that David suggested was meant for 1050 disk drives. (NOTE: David Young, (sorry)). If I am misteaken in any of these statements or beliefs, please someone, correct me. -Richard Hartman max.hartman@ames-vmsb ------
DYOUNG@USC-ISID.ARPA (C. David Young) (02/20/86)
Since there have been two notes expressing disbelief of the "read the first sector" method to switch drive densities, I feel that I must respond. How do you think that a drive knows which density to use beyond sector 3 when it boots a double density drive? I admit I am a little fuzzy on the matter since it has been a good while since I thought about it, but I believe that the first byte of the first sector is the flag that the drive is looking for. I have both a Percom and an ATR8000 and I know that if the drive is not at the right density to read the disk that I have just stuck in the drive I can use OMNIMON to read sector 1 and I am then free to read any other sector on the disk. David Young -------
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.