kevinw%su-dsn@sri-unix.UUCP (11/23/83)
my previous comments are for both 5-1/4 and 8 disks -- but the new ds 8 disks have the index hole in a different place than the ss ones (anyone got a hole punch?). i don't believe that there is any such registration problem on 5-1/4...
brian@sdccsu3.UUCP (11/27/83)
The reason the index hole is in a different place for SS and DS 8" disks
is so that the drive hardware can report to the controller whether there
is a single sided or double sided disk in the drive. Since most if not
all of the popular 8" computers retain compatability with IBM 3740
format, this can assist the disk controller software in making a more
intelligent decision. Some cp/m bios don't even ask what kind of a disk
is in the drive - the make the proper settings based on an identity
sector and the single/double hardware indication (Jade DD is an
example of this). Sure is convenient!
--
-Brian Kantor, UC San Diego
{decvax,ucbvax} !sdcsvax!sdccsu3!brian
Kantor@NoscCENT.MBECK%MIT-OZ@MIT-MC.ARPA (11/29/83)
From: Mark Becker <CENT.MBECK%MIT-OZ@MIT-MC.ARPA>
I've been following the messages regarding index holes in 8"
SS and DS disks. And I'm somewhat confused. I've got a pair of
Shugart 851-R drives. These drives have TWO index hole sensors,
mounted on the same circle that the index hole travels during
rotation. The diskette jackets have a hole punched in them either
under one sensor or the other. Looking at the schematics, I don't
see anything brought out to the PC card-edge that would indicate
to a controller what type of diskette was in the drive.
Brian Kantor brings up the 'identity sector'. My CP/M BIOS
does the same thing; identifies the type of diskette by some value
stored on the diskette. This has a minor backfire if that byte ever
gets altered: you're going to have a problem reading the data off of
that diskette.
--- Mark Becker
ARPA: CENT.MBECK@MIT-OZ
-------CENT.MBECK%MIT-OZ@MIT-MC.ARPA (12/08/83)
From: Mark Becker <CENT.MBECK%MIT-OZ@MIT-MC.ARPA>
Greg -
You're absolutely right. My apologies to the net. On a closer
look at the manual for the Shugart SA850/851 DS/DD drive, jumpering
2S will put the Two-Sided signal onto the i/o connector at pin 10.
However, it turns out that whichever detector is being used, that
detector generates the index pulse.
Mark Becker
ARPA: CENT.MBECK@MIT-OZ
-------brian@sdccsu3.UUCP (12/08/83)
x
On a lot of DS 8" disk drives there is an output (I think its pin 10 on
the standard Shugart connector) that is active (low) when the drive has
sensed a two-sided disk in the drive. Intelligent controllers can sense
this and react accordingly.
On some drives (the MFE and the Qume, I believe) its also possible to
set a jumper option which will make the drive 'not ready' if a single
sided disk is put in it - thus limiting it to double sided disks only.
--
-Brian Kantor, UC San Diego
{decvax,ucbvax} !sdcsvax!sdccsu3!brian
Kantor@Nosc