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From: nick@abccam.abcl.co.uk (Nick Reeves)
Newsgroups: comp.sys.acorn,eunet.micro.acorn
Subject: Re: MODE 21 & MULTISYNC
Summary: Floppy driver turns off video DMA if not enough bandwidth
Message-ID: <680@nick.abccam.abcl.co.uk>
Date: 8 Jan 91 11:28:57 GMT
References: <3800@aipna.ed.ac.uk> <76@hobby.ukc.ac.uk>
Organization: Active Book Company Limited, Cambridge, UK
Lines: 8



The situation as some of you seem to have guessed is that the floppy
driver turns off video DMA temporarily if lack of bandwidth causes an
overun error. Remember that the FIQ for each byte of the sector must
be serviced in 32 us or the whole sector must be retried. This means
that there is a minimum bandwidth needed for floppy operations to be
possible.