Date   : Thu, 10 Mar 2005 11:35:14 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: Anderson Rom Board

On Thu, 2005-03-10 at 02:46 +0000, Mike Tomlinson wrote:
> In article <000d01c524d0$98b08570$d19bbd50@...>, Ken Graham
> <ken@...> writes
> 
> >    Seems the flying lead goes to link S19. As Bruce points out, not 
> >    present on issue 7 boards.
> >     
> >    I have left an image at www.stenswall.co.uk/images/anderson.jpg
> 
> Not a small board, is it?  Some thoughts:
> 
> 1. Although you say it looks new, the circuit design seems to be quite
> an old one, i.e. I think it was designed early in the lifetime of the
> Beeb.  See below for reasons why.

Last chip date I can see is early '84. I wouldn't say the chip sockets
really date it though - turned-pin types are more expensive, and the
type used on this board were/are common enough. At least they're not the
nasty white ones used on very early beebs and are prone to corrosion /
warping :-)

> 3. EPROMs 0 to 3 have more jumper links than the others; the angle of
> the photo obscures the jumper settings printed on the PCB, but I'd
> hazard a guess that they are used to set ROM size (i.e. you can fit 2k,
> 4k, 8k, or 16k ROMs by changing jumpers.)  EPROMs 5 to 15 have a "W"
> link and another link selectable between "F" and "G" (see para 4).

Agreed - although I wouldn't say it sets age of the board, just that the
board was designed to take ROMs that *might* be found in a beeb.

> 7. Wonder why the socket for EPROM 4 is missing?

Ditto. Maybe 0-4 somehow map to the ROM sockets on the BBC mainboard,
and so ROMs 0-3 on the mainboard are supposed to be plugged into 0-3 on
the Anderson board (might explain the extra config available for those
sockets). Maybe whatever's in socket 4 on the mainboard is supposed to
stay there? No idea, just a guess.

cheers

Jules