Date   : Sat, 15 Sep 2007 07:56:42 +0100
From   : dl.harper@... (David Harper)
Subject: Working out disk sizes...

Francis Devereux wrote in response to Jules Richardson:

>> ... just trying to bring up a catalogue using the appropriate ROM (DFS or
>> ADFS) seems like a good start,
>
> Yes, although it can take a while for ADFS to give an error message if you
> try to catalogue a DFS disk (I can't remember how long the other way round
> takes).

I you don't know whether it is ADFS or DFS, then it is definitely best to 
test DFS first. Both filing systems will fail to recognize the other, and 
will eventually come up with an error message (equivalent to the disk being 
unformatted). However, ADFS takes ages to do so. DFS is much quicker.

It is, of course, quite possible for a disk to be formatted in ADFS on one 
side and DFS on the other. The "front" could be ADFS "small" or "medium" and 
Drive :2 could be formatted DFS (though you cannot do it the other way 
round). I don't know whether anyone has ever been eccentric enough to do 
this, but it is quite possible and "legal".

>> (JOOI, what was the definitive ADFS reference for the 8-bit machines? 
>> Whilst
>> DFS seems to have been covered in specific books from both Acorn and 
>> others, I
>> don't think I've ever come across any equivalent for ADFS)

I have never been able to find one either. The most complete seems to be the 
appropriate pages in the Master Reference Manual, but there are still very 
significant gaps that you can only fill in from odd notes in other books and 
(more recently) a few web pages. I have found that, even when you have all 
this lot together, you still have to supplement it by experimenting for 
yourself.

David Harper