Media interchange sillinesss (Was: floppy controller IC (was Re:

From: Jerome Fine <>
Date: Thu Sep 30 22:19:08 1999

>Richard Erlacher wrote:

> Well. . . it wouldn't have made much sense for the folks who made media to
> admit that they were merely charging more for the media marked
> "double-sided" when they were alike in every other way. It seemed that the
> only real difference in many cases was that some diskettes simply were
> priced higher.

Jerome Fine replies:

But that was true for hard drives as well. I remember the story about a Seagate
hard drive - 20 MByte vs 40 MByte - I believe was how the story went. The
20 MByte drive had a bolt in the actuator arm (or something like that) to prevent
use of the extra cylinders. The 40 BMyte drive did not. That is a case of not
supplying as much hardware (one bolt) and charging more.

The 8" flippy (SS diskette) was the same way. You could insert the floppy
upside down to use the media on the other side. Very useful for distribution
or seldom used backup - I was told that turning the diskette in the other
direction tended to dislodge the dirt in the jacket. You supply less of the
jacket (2 extra holes) and charge more.

> The old 8" drives required you punch holes in the appropriate places and
> cover the old ones if you used "single-sided" media in a 2-sided drive,
> having punched the hole, which was the only difference.

I once used a DSD 880/30 as my primary drive (3 * RL02 of 10 MBytes
each on an 8" fixed hard drive) plus a single 8" double-sided floppy drive
(an RX03 or an RX02 if being used as a single-sided drive). Since the
double-sided RX03 was just there to be used, I resorted to punching
holes at first. Finally, I thought it would be worth while to try putting
a double pole/double throw switch into the detection circuit. In one
position, the drive was normal. In the other position, the drive used
the opposite pair of holes as normal. I never used a double-sided
floppy as a single-sided media, but IT WAS GREAT NOT HAVING
feeling the first time I was successful after installing the switch and not
knowing if it would work. By the way, all the media could be used and
read and written as single-sided regardless of how the media was formatted
and written in the first place. The location of the holes did not seem to
matter at all from the timing point of view.

> Since they were available, this swapping of media from one application to
> another happened all the time where I did much of my work back in the
> mid-80's, and I'm not referring to merely a few dozen of each drive type, as
> we were testing and qualifying drives by the thousands. That was pretty
> boring work and, seeing lots of different media, it became obvious when
> there really wasn't a difference other than the label.
> Dick

AND THE PRICE!! EXCEPT, there were about 4000 * 8" media that I tried
to FORMAT on the DSD hardware (NEVER could format on an actual DEC
RX02 of course - DEC always charged about 5 to 10 times the price of
unformatted media) as double-sided. Of all the media I tried, the only ones
I can remember that would not format (just a small percentage - about 5%
which I had received from a company that had tossed the DEC distribution
8" RX02 floppy media - I know Megan - I formatted the RSX-11 software
off the media and never used the programs - I even peeled off the DEC
labels that identified the software) double-sided were DEC labelled
8" floppy diskettes. So while EVERY other media labelled as single-sided
was able to be formatted as double-sided, did DEC actually pay more for
media that were unlikely to be OK as double-sided? I know some of the
pro-DEC people who participate in this group will say that since the media
were specified as being single-sided, I should not even have attempted to
try them as double-sided. But then why did every other 8" single-sided
floppy that I ever tried format as double-sided without any problem?
Tis a puzzle!!

Sincerely yours,

Jerome Fine
Received on Thu Sep 30 1999 - 22:19:08 BST

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