Date   : Thu, 02 Jun 2011 08:58:53 +0100
From   : info@... (Sprow)
Subject: Model B with video corruption

In article <COL120-W16F21639EC2809B38E7CD4837C0@...>,
   paul aslin <station240@...> wrote:

> Also the machine completely hangs if NFS is swapped for DNFS, nothing 
> wrong with the later rom as I downloaded it and used it in an emulator.

Check link S9, it may be sitting waiting for an 8271 NMI to clear.
My money is on NMI problem,
Sprow.