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From: miner@ulowell.UUCP (Richard Miner)
Newsgroups: comp.sys.amiga
Subject: Re: Hard disk through parallel port
Message-ID: <889@ulowell.UUCP>
Date: Mon, 22-Dec-86 00:27:30 EST
Article-I.D.: ulowell.889
Posted: Mon Dec 22 00:27:30 1986
Date-Received: Mon, 22-Dec-86 05:41:57 EST
Reply-To: miner@ulowell.UUCP (Richard Miner)
Organization: University of Lowell
Lines: 27


In several articles lots of people write:
...a disk on the parallel port can be close to the speed of a board on
the expansion bus... - They even mention DMA on the serial port.

A board on the expansion bus can grab the Amiga's bus and blast data into 
memory as fast as it takes to light up the address and data buses and trip
the read/write strobes.  Once the board has the address of an internal data 
buffer the DMA cycle far surpasses an assembly loop reading the serial
or parallel ports.  

When we speak about DMA for hardrives we mean direct access to the systems
bus. The solution is a nice address generating chip and a little 680xx 
bus arbitration logic. Perhapse all on a single LSI chip like the hardware
group at Commodore came up with.

Why are'nt more people taking this aproach?  The logic to interface with
the Zorro bus is not that complex, are address generators that expensive?

PS (to weschester support)
Thanks for the response to manx multitasking question, and great suport
in 86, happy holidays and new year.
-- 
Rich Miner   ...!wanginst!ulowell!miner
Ulowell, Center for Productivity Enhancement        (617) 452-5000 x2693
HAL hears the Amiga9000 series is not selling. "Please explain Dave. Why 
aren't Amiga9000's selling?" Bowman hesitates, "You aren't IBM compatible."