Date   : Sat, 21 Apr 2007 22:33:16 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: BBC Floppies

>Message-ID: <1176723932.11085.5.camel@...>
 
Thomas Drage <drage@...> wrote:
> When I try to save a program in BBC BASIC the computer tells me "Disk
> fault 18 at 00/00".
 
Have you formatted the disk first? Most BBC DFSs don't have a
*FORMAT command built in. http://mdfs.net/Software/BBC/FormDFS.txt
is a format program short enough to be typed in from a printout.
 
> My questions are, will the BBC/this floppy drive read these disks?
> and do I/how do I format them first?
[snip]
 
> However, the strange thing is, that while I am able to read and write HD
> disks on the BBC, if I write an image to a HD disk on the computer
> (using omniflop), the BBC will not read it. If I write a double density
> disk using omniflop, it reads fine. This wouldn't be an issue, if I
> didn't only have two DD disks. Is there any way to say copy the DD disks
> to HD disks using the BBC?
 
You shouldn't be using HD disks to start with, you should be using
DD disks, especially as later on you say they are 5.25" disks.
 
DD disks aren't "low quality" HD disks or anything like that. They
have a completely different disk surface.
 
5.25" DD disks have a magnetic coercivity of 300 Oersteds compared
to HD disks with 600 Oersteds.
 
3.5" DD disks have a magnetic coercivity of 600 Oersteds compared
to HD disks with 720 Oersteds.
 
This 20% difference is close enough so that 3.5" HD disks can
often be successfully used formatted as DD. However, the 100%
difference between 300 Oersteds and 600 Oersteds is to great to
allow 5.25" HD disks to be sucessfully formatted as DD.
 
Office World, Staples, PC World, Maplin, etc., all still sell 3.5"
DD disks, and I have about 2,000 in stock, 20p a throw. 5.25" DD
disks are harder to find, but I have about 3 or 4 hundred in
stock, also 20p a throw.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
United Kingdom Tercentenary : 1707-2007 : http://yr300.org.uk