Current source for RX50 media?

Chuck Guzis cclist at
Sat Jun 25 11:34:00 CDT 2016

On 06/24/2016 09:13 PM, Fred Cisin wrote:

> There are a couple of potential complications to using a 1.2M drive, 
> that can be gotten around in software. (96tpi track spacing, same
> write current, rotational speed and data transfer rate as for 360K)

IBM-style PCs with 1.2M drives use a 300Kbit/sec transfer rate for
double-density floppies.  A tool such as Dave Dunfield's IMD will work
just fine.   The last time I duped a bunch of RX50s, I used Verbatim
"DSDD" media.  Forget about searching for "96 tpi" or "100 tpi" branded
floppies--all that indicates is that verification was performed as part
of manufacturing QA at the indicated track density--it doesn't really
have a bearing on the results.  If a DSDD floppy is good at 360KB, the
chances are overwhelming that it'll be fine in DSQD mode.

As far as ring-less hub floppies go, those are difficult to find and
probably quite old, unless they're specifically labeled (complete with
little arrows) for RX50 use.  Hub rings differ between brands in
thickness; the "clear" type are generally thinner than the opaque (black
or white) ones.

As an aside, the reinforcing ring was originally introduced for early FH
5.25" drives that didn't have circuitry to sense when a disk was being
inserted and activate the spindle motor.  The result that a floppy could
be clamped off-center and mangle the hub area and the data on the floppy
itself.  I remember that Dysan and Verbatim started doing this when the
old un-modified Micropolis drives were in use.  Initially, it started
with a supplied jig and a bunch of self-stick hub rings.  In a short
time, the jig and rings were dropped and floppies simply came with the
rings applied.

As most 8" drives of the time have AC line motors that spin
continuously, this mis-registration was never a problem there.  When
half-height DC-spindle motor 8" drives came out, the problem was already
known in the industry, so 8" floppies don't have the rings.

1.2M (DSHD) floppy drives came much later, after the problem had been
diagnosed and remedied, so those don't *unually* have hub rings.


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