Subject: Re: [BBC-Micro] 32016 + 32082
From: Jules Richardson <[email-masked]>
To: bbc-micro List <[email-masked]>
Date: Wed, 14 Dec 2011 17:07:11 -0600
List-Id: BBC Micro & related machines <bbc-micro.lists.cloud9.co.uk>

Jules Richardson wrote:
> None of my boards have IC16 fitted (just like yours).
> 
> However, none of my boards have a socket fitted for IC6, unlike yours - 
> which might suggest that yours once had something fitted there that has 
> gone AWOL. I don't know if that IC is related to MMU functionality, however.

I manage to track down someone with a schematic for the 1MB board, so just 
as a FYI:

IC6 is supposedly a TBP24S10 - a 256x4 PROM. It's purpose was to correct 
timing on the IRQ and NMI lines, and if it's fitted then LK8 and LK9 are 
supposed to be cut. It's marked as NF on the schematic. The schematic's 
owner thinks that it was only needed to correct a timing flaw in an early 
version of one of the copro's chips, and that a similar issue existed on 
the 4MB board and is mentioned in the ACW service manual. Quite why your 
board (which seems to use quite late parts) has a socket fitted, I don't know.

IC16 is a 74LS365, and is fitted to access the unused 6 links in the LK5 
block. Again, marked as NF on the schematic.

cheers

Jules

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