Date   : Sat, 31 Jul 2010 13:56:39 +0200
From   : rick@... (Rick Murray)
Subject: Why did Acorn ADFS only allow 640KB on a floppy?

On 31/07/2010 11:00, Tom Walker wrote:

> This is largely due to the flexibility of the 177x controllers
 > though... the 8271 (as well as the uPD765/8272 found in PCs and
 > later Arcs) have the gap lengths more fixed.

Ah - wasn't the "standard" DFS based upon an 8271? I think that is what 
was in my Beeb. I recall the adverts in Micro User and the like talking 
about the special 1770 DFS like it was something magical. The FileStore 
uses a 2973 - not sure how (in)flexible that is.

Perhaps the Acorn's smaller 640K discs offered the best reliability 
across a range of different hardware? Remember - at the time their 
target market was in education, it would be important to be seen as 
reliable. I can throw two insults at my FileStore, it is dead slow and 
the front panel is flimsier crap than those 386-era PC cases with the 
silly little 'door'. But it marches on. As does the Beeb with wires 
hanging out. We're getting to the age now where power supplies are 
starting to fail (caps), but rig up other sources of power... the Beeb 
marches on...


Best wishes,

Rick.

-- 
Rick Murray, eeePC901 & ADSL WiFI'd into it, all ETLAs!
BBC B: DNFS, 2 x 5.25" floppies, EPROM prog, Acorn TTX
E01S FileStore, A3000/A5000/RiscPC/various PCs/blahblah...