Date   : Sun, 15 Mar 2009 17:36:21 -0000
From   : mfirth@... (Michael Firth)
Subject: BBC B+ mess up

----- Original Message ----- 
From: "John" <blip@...>
To: <bbc-micro@...>
Sent: Sunday, March 15, 2009 4:51 PM
Subject: [BBC-Micro] BBC B+ mess up


> Hi All
>
> In an attempt to free up some a spare ROM socket for the GoMMC, I've upset
> VIEW.
>
> I've two ROMs that appear to support VIEW, does this sound correct?
>
On the B+, all 16K ROMs will appear in pairs. That will generally mean that 
the same ROM appears in slots 11 and 10, in 9 and 8, 7 and 6, 5 and 4 and 3 
and 2.
If you have any 32K ROMs installed, they will appear as different ROMs in 
the paired odd and even slots, but that tends to be the exception rather 
than the rule.

If you have ROM problems, its worth checking that the 16K/32K selection 
links (S10, S15, S12, S11 and S9, to the left of the ROMs) are all present 
and making good contact.

> Also, I was sure I had the full 128Mb on this board, and now I have only
> 64Mb. I've tried gently pressing down for any loose chips etc.
>
The startup banner to display that its 128K is actually generated by the DFS 
ROM - you didn't remove the 1770 DFS ROM to make space did you?

Otherwise, check the flying lead from the 64K expansion board to S13 (which 
selects whether BASIC is in slots 14/15 or 0/1, and the second 32K of SWR is 
enabled by a flying lead and header that connects to the spare pin of this 
header). The wire to enable banks 13 and 12 of SWR is usually on the back of 
the PCB, so is unlikely to have been affected, unless you've had the PCB 
out.

Try the attached program (I can provide a BBC BASIC encoded version of the 
file if you have a way of getting it onto your machine). It will display 
which ROM banks (if any) are SWRs. For a B+ is should either show 15,14,13 
and 12 as SWR, or 13,12,1 and 0 (depending on the aforementioned S13)

>
> Does anyone have a picture of what the BBC B+ motherboard should look like
> for comparison please?
>
There are two pictures of the B+ motherboard at:

http://bbcmicro.net/old-8bs/inbbcpl.htm

and

http://bbcmicro.net/old-8bs/boards/BBC-B+-motherboard.jpg

The first one looks like its been asset stripped - the VIAs and RAM have 
gone, together with various other components. The second one is actually of 
an ACW (or ABC) motherboard, as it has no analogue video circuitry, and 
vertical IDCs.

On the same site, are some pictures of a B+ with the 64K upgrade, at:
http://bbcmicro.net/old-8bs/see/BBCBplusanddaughter1.jpg and 
http://bbcmicro.net/old-8bs/see/BBCBplusanddaughter2.jpg.

As you can see, there isn't much visible, as all the flying leads apart from 
one go under the PCB.

Hope this helps

Michael 
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