Date   : Mon, 23 Jan 2012 22:13:26 +0100
From   : kortink@... (John Kortink)
Subject: 32016 + ADFS 1.40

Only four years late, this (see thread 'PANOS / ACW user
guide...', Nov 2007), but nevertheless, to whom it may
concern :

After some research into the '32016 + ADFS 1.40' issue,
it has become clear that ADFS 1.40 exists only because
the 32016 (or perhaps just Pandora) can't keep up with
the documented minimum delays for bulk transfers across
the Tube.

In particular, the 24 uS minimum for 1-byte transfers is
simply too much for the poor old 6 MHz 16/32-bit monster.
My experiments with GoSDC (the followup to GoMMC) show
that it needs roughly 8 uS more before the transfers
start succeeding (both read and write).

Re: the thread mentioned, DFS still works simply because
floppies are so damned slow. ADFS doesn't, because it's
pretty tightly coded for HD transfers (9.5 / 25.5 uS best
case for 256 / 1-byte). In ADFS 1.40, Acorn gave these an
extra delay of 12 and 24 uS respectively, just to please
the poor 32016 ... (Seems a tad on the pessimistic side,
according to my tests).

1.40 is the only one that has been 'fixed'. ADFS 1.30 or
1.50 won't do for the 32016. Funnily enough, they actually
do when used as patched filing systems on GoSDC, because
GoSDC does the entire transfer on their behalf. Panos 1.4
loads to the prompt in around 15 seconds.

Anyway, hope that answers some other people's questions,
as well as mine.


John Kortink

-- 

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