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From: emjej@uokvax.UUCP
Newsgroups: net.micro.6809
Subject: Re: OS-9 and double sided disks - (nf)
Message-ID: <3500015@uokvax.UUCP>
Date: Mon, 21-Nov-83 10:49:00 EST
Article-I.D.: uokvax.3500015
Posted: Mon Nov 21 10:49:00 1983
Date-Received: Wed, 11-Apr-84 07:37:12 EST
References: <321@bbncca.UUCP>
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Nf-ID: #R:bbncca:-32100:uokvax:3500015:000:958
Nf-From: uokvax!emjej    Nov 21 09:49:00 1983

#R:bbncca:-32100:uokvax:3500015:000:958
uokvax!emjej    Nov 21 09:49:00 1983

Re side selection on the CoCo: the Frank Hogg method of using double-sided
drives makes each side of a drive look like a separate one-sided drive. The
RS disk controller uses the Western Digital 1793 controller chip, which doesn't
have a side-select pin.

Enough folks are nattering and grommishing (and rightly so, too) about the
current disk driver module, which is tied to the RS disks (it *doesn't* look
at the device descriptors, which would automatically take care of differing
step rates, tracks per side, and the like!) that I think future releases will
do things right (to the extent permitted by the RS controller).

Speaking of the controller--it is a nasty bottleneck, what with programmed data
transfer. If someone would come out with a controller that allowed DMA or kept
a one-sector buffer on-cartridge, or *anything* just to keep from pestering the
6809 every time a byte is transferred, OS-9 would really fly on the CoCo.

					James Jones