Date   : Wed, 05 Sep 2007 09:01:40 +0100
From   : chris.priest@... (Chris Priest)
Subject: Econet oddities and ATPL boards! - Resolved!!

Hi All,

Thought you might be interested in this, I managed to solve my problems 
with my ATPL board and also the econet issues I was having.

I'll start with the ATPL issues.

Turns out the board had been modified, for what purpose I am not sure, 
it had a custom MOS chip in a 27128k chip, pins 1 and 28 had been linked 
by a short piece of wire and the original track to pin 28 cut.

Repairing this and replacing the MOS rom with a standard Acorn one, 
fixed the problems with the ATPL board.

But, I had a new problem!  After a while the beeb would slow down until 
it was unusuable, this occoured even without the ATPL board fitted and I 
couldn't think why.

So, got to thinking.....

This was the machine that I had just fitted one of Ian's excellent 
Econet upgrades to, before you say anything Ian, the kit is fine :)  
What actually happened was this.

I read your instructions to the letter, including disregarding the 
requirement for IC86 I think it was 74LS123 if you had a disc interface 
fitted.  Now I had a disc interface fitted, but it's a 1770 interface, 
one I fitted as an upgrade to what was a cassette based only system, 
IC86? only had a wirelink between pins 8 and 11 I think it was, this was 
a requirement of the 1770 upgrade if this chip was not fitted.

So, I took it for gospel and didn't do anything, unfortunately with this 
chip missing, it caused all of my problems with the econet, including 
random no clock messages, or not working with the terminators fitted 
etc, it also appeared to cause this slowdown issue I was experiencing, 
fitting an 74LS123 kicked the econet into life and touch wood, no 
problems with speed either!

So, Ian, a suggestion, it might be better to say the chip is needed *IF* 
you only have the wire link fitted due to a 1770 upgrade, I appreciate 
the chip exists with a standard 8271 interface.

Anyway, happy bunny, Beeb working on econet and running the ATPL board 
quite happily :)

Anyone care to point out why this modification was required to run a 
custom MOS?  I am not sure on that part.

Best Regards
Chris