Econet (Was: Re: 8-bitters and multi-whatever)

Tony Duell ard at p850ug1.demon.co.uk
Fri Sep 14 16:43:31 CDT 2007


> > It was optional (rather than standard) on almost all Acorn machines. The 
> > only one I know to have had it as standard was the ACW.
> 
> Possibly it was standard on the whole ABC range. It's also fitted on my 310 

Quite likely.

[...]

> > For the 'System' machines, the Econet interface was not suprisingly an 
> > Eurocard you put in a spare slot of the cardcage.
> 
> I've got two variants here (both p/n 200,024) - the earlier one has 
> additional 4017 and LS74 ICs not present on the issue 2 board. Not sure if 
> that was just the collision detection circuitry and they removed it on the 
> later board, or if it provided some other function...

It doesn't sound like collision detection, which used an analouge 
comparator chip (LM319 IIRC). The 4017 is a devide-by-10 ring counter, 
the '74 is, of course, a dual D-type flip-flop. It's either something to 
do with sorthing out bus timing (maybe early 6854s had some oddity here), 
or a way of sourcing the econect clock from that PCB.


[...]

> > Beebs (and B+'s?) had the main PCB laid out fo the econet circuitry, but 
> > no compoennts were fitted. The upgrade was a 'bag of bits' that you 
> > soldered to the main PCB.
> 
> It's funny that the technical spec for the model A/B specifies sockets for all 
> the optional bits, *apart* from Econet; I'm not sure if something can be read 

This has the interesting side-effect that a Model A that's been upgraded 
to a Model B has rather more stuff in sockets than a Model B that started 
out as such.  For example half of the RAM is socketed on the former machine.

I still wonder if it was really worthwhile to miss out the 1MHz bus 
buffers on a Model A and fit sockets in place of them. I can't believe 
the latter were much cheaper than a '244 and '245 :-)

> into that about the BBC's expected take up of the network ability.

Or was it because there were many passive components to solder in anyway? 
Did any of the other upgrads involve anything other than ICs?

>  > The same module is used, IIRC, in the Filkestore systems.
> 
> Quite possibly... I never did take a look inside one. I just had a look at my 

You should have asked when you visited me. I have a Filestore (whatever 
the origianl version with the '2MHz bus connector' on the back is 
called), I would have been happy to take the case off for you... One day 
I'll get round to getting it going. It's missing the floppy drives -- I 
have a couple that will work, but theyre ex-Archimedes machines and are 
therefore lacking ffront panels and eject buttons, and it's misisng the 
front flap, which of course triggers a reflective opto-switch. I am sure 
I can fiddle soemthing to do that, though.

-tony



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