Re: more net notes...

From: Larry Anderson (
Date: 2000-10-14 07:50:50

I was looking for my e-mails on the net ideas and noticed I didn't even
read your reply (it must have been off screen when I recived it...)
Looks like a good idea...  what's the cost in general for such chips and
are they readily avialable still?  I am looking for the low cost method,
will keep doing what I have as it requires only connectors and wires,
but something along the lines of localtalk protocol/topology would be
more usefull for general purpose work.

I am not much of a hardware (electonics) person myself.

Ethan Dicks wrote:
> --- Larry Anderson <> wrote:
> > After a little thought about the throughput of the network (ok, I havent
> > got 'that far', but I like to plan ahead), I am thinking we can get
> > increased speed with more data moved between nodes and less transitions
> > (input to output) than going around the ring with each node's data
> > (packet->in/out/in/out/in/out ->next packet)...
> .
> Have you ever worked with FDDI or Arcnet or any token-based networking
> scheme?  If a token is lost, there is always a mechanism for regenerating
> the token.  Can't go around rebooting servers in a production environment
> just because they lost connectivity for a moment.
> Depending on what you really want to do, there is a one-chip ArcNET solution
> that is as easy to attach to a 6502 as an ACIA - the COM20020.  Dave Haynie
> tried to design it into several Amiga models, only to have management remove
> it due to cost.  His idea was self-terminating RCA jacks (like the ones in
> the front of modern VCRs for audio/video - they short out if there is no
> plug installed (with a termination resistor in the Amiga's case), or if you
> insert a cable, the internal short is opened and the connector passes data.
> A low-tech no terminator solution.  Think of LocalTalk adapters but cheaper.
> If you use an RS-485 driver chip (8 pins, <$1 each), it's possible to build
> a twisted-pair, multidrop ArcNET network.  The COM20020 has built-in buffer
> RAM, enough for a full packet.  You don't have the same problem with data 
> underruns because of how ArcNET works.  It's not broadcast like Ethernet.
> It all depends on what you are really trying to do here, but if a hardware
> solution is called for, consider this chip.  There's a schematic I worked
> on *years* ago (1987?) for an Amiga parallel port ArcNET adapter.  I never
> built one and we never wrote drivers, but I got questions about it for several
> years.  I'm pretty sure it's on AmiNET.  A search for pocket.lzh might turn
> it up.  It's not much more than a COM chip, a line driver and a crystal.
> Easy as pie.  The software is another matter entirely.  You'd still have to
> implement some kind of protcol stack for the higher layers, but at least
> you would be able to get bits from one box to the next from the get go.
> Other schemes might make more sense if they only require a cable and possibly
> a line buffer.  Depends on the goals.

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