Date   : Mon, 06 Nov 2006 04:14:47 -0600
From   : julesrichardsonuk@... (Jules Richardson)
Subject: DFS on 3.5inch - Is this supposed to work?

Jonathan Graham Harston wrote:
> Another matter to know is that very few PC disk controllers can
> actually do single density encoding. The vast majority only
> understand MFM and many PCs have crippled BIOSes that only allows
> reading and writing of 512-byte sectors.

Yep. PCs always used MFM encoding from day 1 - it was about the only good 
design decision that IBM made when it came to the PC, but why they didn't 
include the ability to read/write FM too I don't know. Much of the world was 
still using systems which only understood FM at that point, so the ability for 
users to upgrade to a PC and migrate all of their data would have seemed like 
a good marketing decision at the very least.

A handful of PCs will *read* FM data OK, but finding one that will actually 
*write* it too is a real challenge.

> High density records data at 500kHz - twice low density.

Although I suppose you could under-sample at a lower data rate, although why 
anyone would want to do that I don't know :-)

cheers

Jules