Date   : Tue, 31 Aug 1999 23:00:32 +0100
From   : Philip Blundell <Philip.Blundell@...>
Subject: Re: and onto Beeb no 2 

>This is with the NMI (S2) disabled. When it is enabled, with all 3 chips the
>beeb hangs. When the beeb hangs the 68b54 interrupt line is stuck low.

Check for the NMI line shorted to ground?  I can't think of any more 
suggestions without looking at the schematic I'm afraid. :-(

The NMI also goes through some gating logic which could be suspect but I 
can't remember where exactly that lives off the top of my head.

p.