Date   : Fri, 06 Oct 2006 16:01:37
From   : "Ian Wolstenholme" <BBCMailingList@...>
Subject: 3.5 inch floppy DD/HD compatibility

Sorry if this is going over old ground, but I am trying to get my
head round what 3.5" drives and discs are likely to work reliably
with Beebs.

I know that HD discs won't work even when using a 3.5" HD
drive, I believe this is because the data transfer rate for HD
format is twice as fast as DD and it's too quick for the Beeb.

I also know that DD discs will work in most HD drives because
they can detect a DD disc and switch to DD mode.

So far so good - and please correct me if any of the above is
wrong!

I understand that you can cover up the second hole on an HD
disc to trick the drive into going into DD mode, and that some
drives have density jumpers so you can set the drive to always
operate in DD mode no matter what disc you put in.  This is
said to be "unreliable/not recommended" etc. but I don't
really understand why.  Can anyone elaborate in layman's terms?

The trouble is that it seems that getting hold of 720K 3.5"
discs is harder than 5.25" discs and even 8" ones!!

Best wishes,



Ian