Date   : Sat, 31 Jul 2010 20:07:02 +0100
From   : tom@... (Tom Seddon)
Subject: Why did Acorn ADFS only allow 640KB on a floppy?

On Sat, 31 Jul 2010 03:39:22 +0200, you wrote:

>On 31/07/2010 00:55, Tom Seddon wrote:
>
>> offer(ed) 720K discs, using a normal 1770 FDC. 2 sides, 80 tracks, 18
>> sectors per track, 256 bytes per sector. Don't know why this layout
>> wasn't more popular, but perhaps there's a good reason.
>
>Does anybody here have the timings (especially GAPx) for the 18 sector 
>type format(s)?

That's an interesting question...

Looks like there is some info on the Beeb Wiki:

http://beebwiki.jonripley.com/Opus_DDOS

"The *FORMAT command built into DDOS specifies gap1 = &24 and gap 3
&1B, to write respectively 36 or 27 bytes of &4E plus the required
synchronising sequence; and gap5 = 0, which eliminates the pre-index
gap and the index address mark."

--Tom