3B2 memory, floppy drive

[Michael Wendel]

In article <1990Jan17.062113.16770 at robohack.UUCP>, woods at robohack.UUCP (Greg A. Woods) writes:
> In article <11033 at attcan.UUCP> ram at attcan.UUCP (Richard Meesters) writes:
> > In article <860 at red12.qtp.ufl.edu>, taylor at qtp.ufl.edu (Charles Taylor) writes:
> > >   1. Is the floppy drive that came standard on the machine a 360K or
> > >      1.2 Mbyte floppy drive and which device do I use to address it
> > >      as a 1.2 Mbyte drive? (if applicable).
> > >
> > The 3B2 line uses a 720K floppy drive, You must use 96tpi double or high
> > density diskettes with this drive, and you are better off if you use the 
> > high density media ( more reliability ).
> 
> Sorry Richard, but it's best if you DON'T try to use HD (high density)
> diskettes.  If I remember right they have been specially formatted
> during the manufacturing process in order to help the IBM PC/AT (and
> compatible) drives to seek to the centre of the track (remember when
> they cost $150 per box?  I sure do!).  This factory formatting is
> quite difficult to erase, and in any case, I've had no luck trying to
> use HD diskettes (when I was short of diskettes, I tried quite
> desparately, on three different 3b2/400's, and on a 3b2/300 to format
> some with no luck).
> 
> Your best bet for 3b2 floppy media is to use a known reliable brand of
> DS/DD (48tpi) diskettes (because they are cheap and easily available),
> and always format with error checking and write with verify.  All
> diskette media comes from the same cookie cutter.  The label
> identifies the degree to which it was tested.  Some manufactures
> downgrade the rating of cookies which fail the more stringent tests,
> and others simply junk the cookie.
> -- 
> 						Greg A. Woods

Still more confusion added to this. The 3B2 uses 720K floppies. This
requires the DS/DD 96tpi floppy disks. These are not the DS/DD 48tpi
(360K) diskettes and these are not the DS/DD HD (1.2MB) diskettes.
They are a unique lot with a limited base of users. The AT class
of machines leapfrogged to the HD (1.2MB) diskettes from the 360K
diskettes skipping the 96tpi lot. As for the problems described above
when using HD diskettes, this is true. You can try them, but you will
find that most of the time it won't work. Not only is the format
different, but the media magnetic properties is different, and that
is why you can't reliable erase the manufacturers format with a 3B2.

As for using the 48tpi diskettes, the drive is capable of reading 
and writing these diskettes, but AT&T did not provide any software
or driver interface to do this. You are stuck with 96tpi, 720K.
There is a company in Austin TX, Congruent Technologies, that wrote
a driver for using 360K, 48tpi diskettes. But I only think it uses
DOS formatting (ie. it is for reading and writing DOS disks on 3B2).

I have several 3B2 systems, and they have been one of the MOST RELIABLE
systems I have ever worked on, or programmed on. But the early models
(300/310/400) had the lousiest floppy and tape systems, primarily due
to the lack of following a popular industry standard. 96tpi disks
are VERY expensive compared to HD (1.2M) diskettes. What makes HD
disks cheap, is the market base that buys them. It is much larger
than those that use 96tpi. As for the tapes systems, another story,
AT&T used the Floppy Tape, where you put 23MB on a tape capable of
holding 60MB AND the tape could only be read on AT&T machines that 
used this Floppy Tape format.....


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Michael L. Wendel     (602) 464-5744                                  /\
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