Date : Sat, 26 Apr 2008 15:14:38 +0100
From : C.J.Thornley@... (Chris Thornley)
Subject: Reviving a dead BBC+
Hi,
Do you have a schematic / Block Diagram showing how you have contented
things together? I am presuming the two RAM chips are both are in parallel
and the chip select line is used as an address line for the second chip?
What does the ARM 1.12 ROM do? Rom 07?
I am not to sure if the GOMMC boards are still available for the B+ as I
believe there where some bugs to still be ironed out with the B+ last time I
enquired.
Chris
/> Christopher J. Thornley is cjt@...
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-----Original Message-----
From: bbc-micro-bounces+c.j.thornley=coolrose.fsnet.co.uk@...
[mailto:bbc-micro-bounces+c.j.thornley=coolrose.fsnet.co.uk@...
uk] On Behalf Of Ken Lowe
Sent: 26 April 2008 11:35
To: bbc-micro@...
Subject: Re: [BBC-Micro] Reviving a dead BBC+
Ken Lowe wrote:
>>>I intend to get hold of another 32K RAM chip and build a small
>>>circuit board that will hold both 32K RAM chips, and a single 32K ROM.
>>>This circuit board will then plug into one of the existing ROM
>>>sockets, with flying leads to the three external points highlighted
>>>above, and a fourth to pick up page 0/1 select. This should provide
>>>me with a fully expanded 128K B+ with all ROM sockets still available.
>> Very nice :) I'd like to see photos of that if possible.
> I'll post up some pics once I receive all the bits (waiting on 28 pin
> sockets and RAM chips). Initially I'll build it on breadboard, so it
> might look a bit messy. If it works as I expect, then I might make a
> proper PCB to make it look a bit neater.
Ok. It's all up and running. Photos are here:
http://i300.photobucket.com/albums/nn18/chaser2001a/BBCPLUS128K/PICT1020.jpg
http://i300.photobucket.com/albums/nn18/chaser2001a/BBCPLUS128K/PICT1019.jpg
http://i300.photobucket.com/albums/nn18/chaser2001a/BBCPLUS128K/PICT1030.jpg
http://i300.photobucket.com/albums/nn18/chaser2001a/BBCPLUS128K/PICT1052.jpg
http://i300.photobucket.com/albums/nn18/chaser2001a/BBCPLUS128K/PICT1053.jpg
http://i300.photobucket.com/albums/nn18/chaser2001a/BBCPLUS128K/IMG_1351.jpg
The left most socket on my board is a direct replacement for the host socket
(IC62) on the mainboard. The other two sockets contain the 32K RAM chips,
both of which can be write enabled / disabled using the connected switches.
My board doesn't actually need to be plugged into the IC62 socket - it can
be plugged into any of mainboard ROM sockets (apart from the BASIC / OS ROM
socket, obviously). I may need to move my board if / when I get a GoMMC for
the B+.
> I've also ordered some bits to build an eprom programmer so I can
> create a 32K ROM with both ADFS (for my HDD), and DFS. I don't have
> the standard B+ DFS1770 V2.22 on EPROM and currently I'm having to
> copy it from my HDD into the upper half of my new 32K RAM bank in
> order to see the ACORN OS 96K message.
Built the EPROM programmer too using this
http://www.bbcmicro.net/old-8bs/submit/subeprog.htm. I didn't bother with
the voltage regulator part of the circuit - instead I used a spare 12V
supply that I had lying around. Decided not to take photos of it. It's built
on breadboard, and looks a little messy! I had to modify it slightly to
program 32K EPROMs (basically I programmed 2 x 16K banks). You'll see that
I've created a ROM with ADFS1.30 & DFS2.22. I made ADFS the higher priority
ROM because I prefer to boot to my HDD. DFS 2.22 gives me the SRAM utilities
and allows the boot up screen to show the amount of sideways RAM installed
(now saying ACORN OS 128K when both write protect switches are in the write
enable position).
Ken.
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