Date   : Sun, 07 Aug 2005 14:06:00 +0100
From   : Phil Blundell <philb@...>
Subject: Re: Econet Bridge

On Sun, 2005-08-07 at 13:16 +0100, BeebMaster@... wrote:
> The Acorn Econet Bridge I bought from Chris Johns off E-Bay
> has arrived and it is slightly interesting inside because the top one
> of the 2 68B54 chips is in fact a 6854 which I understand is the 1MHz
> version as opposed to the 2MHz 68B54 version and the top one of
> the two 26LS30 chips is a 26LS34.
> 
> I wondered if the Bridge had been modified to run with a "slower"
> network, say a System or Atom network?
> 
> Or maybe it was just a question of replacing dud parts with what
> was available at the time.

Most likely the latter.  The 68B54 has no minimum frequency: it will run
quite happily at 1MHz, and/or on a slower network.  But, assuming the
bridge only uses a 1MHz clock, the 6854 (or 68A54, which was a 1.5MHz
version) would be an adequate replacement for the 68B54.

p.