ISA ( PC ) 8" floppy disk CONTROLLER ???

Fred Cisin cisin at
Wed Feb 4 14:45:07 CST 2015

> > I've seen the wiring info in the manual and I just looked through the PDF
> > version of the manual I have. I could not find any mention of TG43 in my
> > quick look through. Do you by any chance know where the info is? Thanks.
On Wed, 4 Feb 2015, Chuck Guzis wrote:
> TG43 is also sometimes called "RWC" for reduced write current.  On many
> later 8" drives, this is a NC.

On inner tracks on a constant speed drive, the data is closer together.
Therefore, the reliability is lower.
(Some variable speed drives will change speed and write less data
on inner tracks)

One effort to help a little is "write precompensation".  On inner
tracks, if adjacent flux transitions that would end up real close
together are written slightly out of position, slightly further
apart, it can help reduce the problem of flux transitions being
too close together.  As part of doing that, there is a signal
available called "TG43" ("track number greater than 43") to help
decide when to enable precomp.

It is NOT needed for reading, but is sometimes used to enable
precomp for WRITING.

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