Date   : Sat, 25 Jul 2009 22:24:51 +0100
From   : pete@... (Pete Turnbull)
Subject: Econet Clocks and Modules

On 24/07/2009 20:01, Rob wrote:
> I've been having fun and games wth my real-econet today... trying to
> isolate what's working, what's not, and why...   I seem to have two
> rock solid Model Bs, some unreliable Masters, and an unresponsive
> A5000...
> 
> Quick questions ...
> 
> Why would a Master 128 talk very very very slowly (10-15 secs to reply
> to *I AM) to a Model B running L2 whereas another Model B logs in
> instantly?  Faulty module?  Clock speed?

A Master should, all other factors being equal, be able to very slightly 
outperform a B.  If it's very slow, it could be a faulty module, or one 
that is lacking the collision detect circuitry (which matters most if 
the rest of the net is below par).  The A5000 takes the same type of 
module as a Master.  If everything is OK, the A5000 should be capable of 
handling much higher clock speeds than the M128 or Beeb.  Maybe 
something is up with the clock or termination.  See below.  I've also 
seen this effect on a large network where some of the cabling was of 
poor quality (and had a lot of poor joints), but I'm guessing your 
network is not several hundred meters long :-)

> Can I just plug a lead into one socket on an acorn clock box 2, or do
> I need to use both, and is it because I left one empty that I was
> getting Line Jammed errors with both boxes?

On the black clock box that has two connectors, each socket is fed from 
a separate clock source, and only the data lines are passed through. 
The idea is that you split the network at or near the centre and use the 
clock box to bridge the two halves, each of which must be terminated.

If you only use one socket on the clock box, then of course you can just 
plug it in to any other network socket.

Line Jammed is usually either a faulty unit on the net, holding the 
signal lines at an improper level, or is the result of a missing 
terminator.  However, it can also be caused by reflections if your 
network is T-shaped with a long extra arm (it should be linear, one line 
from end to end), but this is rare.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York