Path: utzoo!utgpu!water!watmath!clyde!att!att-ih!ihnp4!ucbvax!CORY.BERKELEY.EDU!dillon
From: dillon@CORY.BERKELEY.EDU (Matt Dillon)
Newsgroups: comp.sys.amiga
Subject: Re: AppleTalk, Networking, Amigas and Offices
Message-ID: <8804260717.AA24693@cory.Berkeley.EDU>
Date: 26 Apr 88 07:17:29 GMT
Sender: usenet@ucbvax.BERKELEY.EDU
Lines: 26


>Now, is there ANY way to use the BLITTER to get/put data from one address
>into/outof memory.  If the system could DMA the data you could have a very
>fast parallel port (assuming that you got the data in the short period
>before the next byte was written.)  I assume that one problem would be the
>need for chip memory.  Comments?

	The question is, how to create a local area net without buying
(or designing) a real-life DMA driven auto-configuring board.  The problem
is really how to deal with multitasking.  One could write a fully 
handshaking scheme driven by a task over the parallel port that would
have an aggregate throughput on the order of, say, 60 to 100 KBytes/sec.
Over the serial port, a fully handshaked scheme could run at about 
26KBytes/sec.  Using an audio channel, one could easily output a 16 symbol
set at 28KBaud = 14KBytes/sec (assuming the filter is turned off), though 
getting data back would pose a problem.

	Now, one must deal with multiple machines on the network.  One
cannot simply connect multiple TTL/CMOS outputs together.  Usually something
like an open collector buffer is used (wire-and).  The serial line has
the fewest number of wires ... two, thus two o.c. drivers.  The network
itself would be a single data wire and a single ground reference.  
Alternately one might want to capacitively couple the network instead of
using O.C. drivers....  now if only I had some time...

				-Matt