Date   : Thu, 25 Oct 2007 08:55:51 +0100
From   : pete@... (Pete Turnbull)
Subject: Teletext adaptor ROM?

On 25/10/2007 08:47, Adam Sampson wrote:
> Pete Turnbull <pete@...> writes:
> 
>> PB04 is the MOS and PB05 is BASIC-II.
> [...]
>> 201666 is the DNFS ROM.
> 
> Ah -- that makes sense! Neither machine has Econet, and upon closer
> examination the dead machine's missing the 8271; it's clearly been too
> long since I had a BBC apart...

If it has no 8271 but S9 is open, that might account for the failure to 
work.  S9 enables the NMI from the disc controller; without it, and no 
controller, it will be getting a continuous non-maskable interrupt.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York