4 Oct
1999
4 Oct
'99
1:03 a.m.
> > Hey, with the discussion of diskettes
recently, and my own
> > search for info on RX50's, I was a little surprised by the
> > lack of available info on single-sided single-density 5.25"
RX50 is single sided double density 5.25 using common media used for other
5.25 drives. It was a 96tpi drive, 400kb. DEC formatted that media 10
512 byte sectors per track and a 1793 FDC a must to recreate that format
reliably.
QD is a misnomer, it really means DSDD 80-track, and
the figure of 720K
relates to 9 sectors per track, 512 bytes per sector.
QD was 96tpi TWO SIDED. There were two formats, 720k and 780k.
Finally, the number and size of sectors can be varied.
IBM happened to use
9 sectors per track (8 on early systems, hence the existence of 320K disks
as well as 360K) with 512 bytes per sector, MFM. Other manufacturers did
This is PCism. CPM systems used 256/512/1024 byts sector and different
sectors per track with 10x512, 9x512, 16x256, 18x256, and 5x1024 being
some of the more common for DD (MFM) modes.
> that worked fine as SSSD failed miserable in the
Tandy 2000 (720k)
> while others worked just peachy. I don't know of any failures
This was usually cleaned up by bulk erasing the media.
There were three basic soft sector medias, 35track (small window for
head), 40 track (larger window) and the 600o 1.2mb. Obviously there were
flavors of single and two side good media. Most large window was two
sides good and worked in everything save for the odd 1.2mb drives.
Now... how the floppy controlers were programmed tended to make or break
systems. The PC controllers are all 765 based and will not always do some
of the odder formats well (or at all!).
Allison