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From: louie@sayshell.umd.edu (Louis A. Mamakos)
Newsgroups: comp.sys.amiga
Subject: Re: Hard disk through parallel port
Message-ID: <1404@umd5>
Date: Tue, 23-Dec-86 11:56:08 EST
Article-I.D.: umd5.1404
Posted: Tue Dec 23 11:56:08 1986
Date-Received: Wed, 24-Dec-86 00:04:00 EST
References: <634@hp-sdd.HP.COM> <1121@cbmvax.cbmvax.cbm.UUCP> <1527@ulysses.ho <2241@well.UUCP> <8088@topaz.RUTGERS.EDU>
Sender: uucp@umd5
Reply-To: louie@sayshell.umd.edu (Louis A. Mamakos)
Organization: University of Maryland, College Park
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In article <8088@topaz.RUTGERS.EDU> eric@topaz.RUTGERS.EDU (Eric Lavitsky) writes:
>In article <2241@well.UUCP>, bj@well.UUCP (Jim Becker) writes:
>.>In article <1527@ulysses.homer.nj.att.com> eric@ulysses.UUCP (Eric Lavitsky) w
>rites:

>>The Parallel port doesn't have DMA, but the serial port does. Noone has tapped
>>this yet though. It will be inconsiquential though, when the Pal Jr comes out
>>there will be a new standard that will take a while for the human to get 
>>used to, especially with InfoMinder Plus.
>
>Yes, but to tie up the serial port with a hard disk would be a very
>big mistake - one often wants his disk available while online with
>another host, you could always wait for the printer, right? :-)
>
Hmmm.. from all that I've seen, the serial port doesn't do DMA.  It just
generates interrupts.  Both the hardware manual and disassembly of the serial
driver seem to bear this out.  It's a real shame it doesn't.

In any case, another issue to examine when considering a DMA disk vs. an
interrupt driven one is the effect on the rest of the system.  Even though
the bandwidth to the disk is the same, the DMA design should all the CPU time
to service other tasks in the system.  The non-DMA version will consume more
CPU resources to get its job done.

Ain't this multitasking just grand?  A computer that can walk and chew gum at
the same time!
Louis A. Mamakos  WA3YMH    Internet: louie@TRANTOR.UMD.EDU
University of Maryland, Computer Science Center - Systems Programming