Re: NadaNet (was Re: brad w. Re: Ethernet & Internet on Apple 2)

["Bill Garber" <willy46pa@comcast DOT net>]

"Michael J. Mahon" <mjmahon@aol.com> wrote in message
20040703115957.25422.00000956@mb-m29.aol.com">news:20040703115957.25422.00000956@mb-m29.aol.com...
: Ed Eastman asked:
:
: >>Michael J. Mahon wrote:
: >>They boot over the network from the "master" machine,
: >>...
: >>The latest protocol addition was the network boot protocol,
: >>  required to use machines that have no attached peripherals.
: >>It currently works perfectly with two or three slaves, but
: >>with a larger number (six), I have found that my original
: >>idea for generating a (really) random ID at power-up is not
: >>as random as I hoped.
: >
: >Why not have the 'master' IIe or the msg server IIe assign
numbers upon
: >request.  Make the request part of the initialization or Boot
process.
: >(Sorry, random thoughts.)
:
: The master machine _does_ assign ID numbers.
:
: The problem is that the machines must be distinguished in order
: to communicate at all, since both arbitration and addressing
: are based on an ID (temporary for boot, permanent after).
:
: Otherwise, if two boards choose the same temporary ID, they
: will forever attempt to communicate simultaneously and will
: respond in lockstep to any message addressed to them,
: preventing later disambiguation.
:
: My problem was in obtaining a unique temporary ID so that
: the master could assign a permanent one through protocols.
:
: Many other network schemes use some unique address
: built into the interface to prevent an endless loop of
deterministic
: collisions.  I hoped that I could use the (presumed) undefined
: initial state of the video refresh generator to create the
needed
: non-determinism.  That assumption turned out to be wrong.
:
: Since I was already using Paddle 3 as a pulse-stretcher for
: a "send" LED on each board, I have now varied the paddle
: resistor value just enough to guarantee unique paddle 3 read
: values, which the boot ROM now uses to generate its temporary
: ID.  Problem solved--but I had hoped to do all boards
identically.
:
: Because of the rather large tolerance on the paddle timing
: capacitor, it is necessary to keep a record of the Paddle 3
: value for each board, and to install a resistor that produces
: a unique value.  ;-(
:
: A less elegant solution, but it works well with six boards.
;-)

Now a bigger problem exists. You've created a system which
requires somewhat of a technician to install and set up. :o)

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - willy46pa @ comcast DOT net
Change DOT to a dot to contact me



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