Floppy disks again

From: allisonp_at_world.std.com <(allisonp_at_world.std.com)>
Date: Wed Oct 13 07:34:46 1999

> The reason the manual says "Use only formatted RX50 diskettes" is that
> formatting the 10 sectors/track on an RX50 is rather critical, and most DEC
> machines to which those drives were connected, weren't supplied with
> formatting software. Rainbows were, though (I think), and I regularly
> format RX50s on other machines.

Two reasons DEC did this. One was they believed the RX50 was to "sloppy"
to format reliably and most of the smaller controllers used with it ran
out of rom and couldn't fit the formatter. Add to that a generally weird
attitude about formatting media in the field.

> > ???? 720K,96tpi,80tracks/side - What was (is) this called? DSQD?
>
> The number of tracks has nothing whatsoever to do with the density! RX50
> is SSDD, it just happens to have 10 sectors of 512 bytes per track, and 80
> tracks. Your "??? 720K" is DSDD. Yes, some people did call this QD, but
> it isn't a different density at all -- the misnomer comes from people who
> don't understand what the words mean. Your numbers for 180K, 360K, etc,
> assume a particular number and size of sectors, which need not be the case
> (ie you can use the same drive and media to make a disk of different
> capacity).

Misnomer, but back in the early 80s when it appeard on CP/M system it was
indeed called that to reflect not the format but the capacity wich was
quad (four times) the single density floppies. I know when NS* offered
the DD controller one option was 96tpi twosided drives and it was called
quad density as it was 800k and the same controller single density on
a 35track single sided (the introductory format) was a whopping 90k!

Allison
Received on Wed Oct 13 1999 - 07:34:46 BST