DSQD Drives (Was: RE: Diags/Boot image for Altos 580)

From: Richard Erlacher <edick_at_idcomm.com>
Date: Sun Mar 17 13:09:54 2002

I think you fellows may be woofing up the wrong tree. The normal DRIVE does
not determine what the modulation scheme is. GCR, MFM, FM, etc, are
modulation schemes. The drive simply takes what's sent to it and divides it
by two, thereby producing a single flux reversal for every positive transition
in the data stream. You can send it NRZ, Manchester, or RLL, or whatever you
like, but it will only take the data stream you send it and produce a flux
reversal for each positive transition. On read, if the data you sent it was
at the right frequency for the head/media combination, and had the minimal
number of transitions per unit of time, (that's why NRZ generally doesn't work
over time) you'll get back more or less what you sent it, less write
precompensation.

There are exceptions to these principles, but only in environments where the
system vendor chose to provide a non-standard drive, e.g. as Apple has, in the
past, chosen to do.

I can't tell you what the ALTOS 58x boxes do, since I gave mine to Will
Jennings some time back. That one had a CMI 32 MB drive in it, IIRC and a
96TPI (?) HH FDD.

Dick

----- Original Message -----
From: "Douglas Quebbeman" <dhquebbeman_at_theestopinalgroup.com>
To: <classiccmp_at_classiccmp.org>
Cc: "'Doc Shipley'" <drdidlittl_at_yahoo.com>; "'Marvin Johnston'"
<marvin_at_rain.org>
Sent: Sunday, March 17, 2002 11:33 AM
Subject: RE: DSQD Drives (Was: RE: Diags/Boot image for Altos 580)


> > I just took a look at the docs for the Series 5 Altos computers and
> > there is a repair ticket for a Mitsubishi M4853 Disk Drive. The floppy
> > disk summary docs indicate that drive is a 5.25, HH, 720K, 96
> > TPI drive.
>
> Ok, not GCR, but I suppose similiar to drives used
> in the Sanyo MB550 (or whatever that silver incompatible
> was called).
>
> > The CP/M version with my Altos 580 is 2.2 Licensed from Digital Research
> > by Lambda Software (4 disks.) Each of the six disks I have are labeled
> > double sided, double density, soft sectored. Of the two other disks, one
> > is for the 580-20 and is labeled MPM/CPM for Altos 580-20, the other
> > Altos Diags for model 580-x.
> >
> > Hope this helps!
>
> Can you make copies for Doc?
>
> Regards,
> -doug q
>
>
> >
> > Douglas Quebbeman wrote:
> > >
> > > > IIRC the Floppy on an Altos 580 is DSQD.
> > >
> > > Am I correct that while different from standard
> > > DSDD, they are *not* GCR drives?
> > >
> > > What other machines might carry these drives, can I
> > > hook one up to a standard PC controller in a box
> > > running DOS, and then duplicate the disks?
> > >
> > > > I had one that had the CMI hard drive replaced with a
> > Seagate ST225. So I
> > > > know they will take similar configured Hard Drives. I
> > think they will take
> > > > 10, 15 and 20 Meg HDs.
> > >
> > > This is good to know, ST225s still pop up from time to time...
> > >
> > > -dq
> >
>
>
Received on Sun Mar 17 2002 - 13:09:54 GMT

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