Date   : Sun, 16 Dec 1990 18:23:54 GMT
From   : att!fang!alfred!tous!tarpit!bilver!bill@ucbvax.Berkeley.EDU (Bill Vermillion)
Subject: uniform and 8 inch cpm formats on AT controllers

In article <"14-Dec-90.22:31:53.EST".*.Michael_D._Sprague.wbst311@Xerox.com>
sprague.wbst311@xerox.com writes:
>
>> The 1.2M floppy format uses the same data-transfer rate as an 8" drive
>> (500Kbits/sec). This is also true for 1.44M drives.
>
>> 360K floppies use the standard 250Kbits/sec.
>
>Hmmm, I knew both of those, but what is the transfer rate for a quad density
>drive?  I assume 250K bits/sec?
>

"Quad density" is a mis-nomer.  It started many many years ago when someone
(I think it was Micropolis) was able to reduce the step positions reliably.
The first drives were 100 tpi (that's right), later to become 96 tpi so
that you could double step  96 tpi to read 48 tpi disks.

"Quad density" is an advertising gimmick that stuck.  It is nothing more
than double density with twice the tracks, erg "quad capacity" should have
been the name.  Transfer rate is the same 250K/bits/sec.   8" single
density is also this rate, only the DD use 500k, which was only about 15%
slower than first PC hard drives

-- 
Bill Vermillion - UUCP: uunet!tarpit!bilver!bill
                      : bill@bilver.UUCP