Shugart SA850/851 8" floppy drive

From: Richard Erlacher <>
Date: Fri Feb 2 19:49:29 2001

Hey, Tony!

I've got lots of Shugart doc's, but the 85x are conspicuously missing. If
you have a scan of this document set, I'd certainly like to add it to my
collection. This stuff, once scanned and cleaned up, will be put on a web
site, ostensibly, that's still being set up.

Can you help out here?



----- Original Message -----
From: "Tony Duell" <>
To: <>
Sent: Friday, February 02, 2001 11:47 AM
Subject: Re: Shugart SA850/851 8" floppy drive

> >
> > We have a collection of test programs stored on 8" floppies which were
> > of a Fairchild F70
> > PCB tester. We're trying to convert them to be read by a PC.
> > A field Eng. from Schumberger (who took over the Fairchild tester
> > line) tells me the
> > 8" drive was a Shugart SA850/851.
> Well, I have the SA850 service manual somewhere. I could probably even
> find it...
> > We need to know the format information. We have a couple of old 8"
> > drives, but can't seem to make out the format. I noticed in one of the
> But it's not going to help with the format information. 8" disk drives,
> like virtually all floppy drvies have a 'raw' (low level) interface. It's
> up to the _controller_ to determine the format.
> The disks could be soft-sectored (one hole for the index sensor) or hard
> sectored (one hole for the start of each track, evenly spaced, and one
> hole midway between 2 of them for the index).
> The data could be recorded using FM encoding ('single density'), MFM
> encoding ('double density') or a number of other less widely-used methods
> (MMFM, GCR, etc).
> Even when you've worked out those details, you still have to find the
> number of sectors/track, the size of each sector, and other similar
> information. If the controller was custom (as opposed to using one of the
> standard disk controller chips) then the sector headers could be just
> about anything. Heck, I've seen machines using FM encoding for the
> headers and MFM encoding for the data...
> And after that you've only managed to read raw sectors. You then have to
> work out what sectors make up a given file -- things like the directory
> format (assuming there is a directory), etc.
> The best place to start looking would be in the service manual/schematics
> for the instrument itself. You should be able to work out what the very
> -tony
Received on Fri Feb 02 2001 - 19:49:29 GMT

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