[BBC-Micro] Reviving a dead BBC+
ken.lowe at btopenworld.com
Sat Apr 26 11:35:12 BST 2008
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
> make it look a bit neater.
Ok. It's all up and running. Photos are here:
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
> 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
> the upper half of my new 32K RAM bank in order to see the ACORN OS 96K
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
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