exxos's Atari, Amiga & retro forum

Well, I finally got to unpacking and a bit of cleaning. Overall everything is in fabulous order and was clearly well looked after. Here's the money shot:


So, we have:

A BBC Model B, Issue 7 mainboard and InterWord ROM based word processor and RGB cable, most likely for a Microvitec Cub.
Cumana double 5 1/4" floppy disk unit with manual and disk.
Heavy duty steel monitor stand.
Acorn cassette unit with manual, cables and 5x cassettes including Chuckie Egg :)
User manual and introductory software pack on cassette.
InterWord packaging and manual.
Software disk (Contents unknown)
Citizen 120D dot matrix printer with all cables tractor feed and a pile of tractor feed paper!!
A Gunshot joystick specifically for the BBC as it comes with an adapter.

I've given it all a basic clean up and it's all come up very nicely indeed and was clearly looked after by the previous owner.

Next on the cards is to get the RIFAs replaced in the PSU. Last time I had RIFAs go off (The ICL OPD), it took a good month to get the smell out of the office/workshop, so they're getting replaced before they have the chance to fail!!

I'll also pull the top off the Cumana unit and clean the mechanism and heads before I give it a go.

The only bad bit is the 'ashtray' to the left of the keyboard which has been pushed through, though I might see if I can get a period correct ZIF socket to fit there.

Interesting computer.

Wat is the use for the "ashtray" connector, is it a kind of user port connector?

The only picture I could find is the one on this site:
http://www.computinghistory.org.uk/det/ ... A-Issue-1/

Maximilian wrote: 29 Jul 2022 09:23 Wat is the use for the "ashtray" connector, is it a kind of user port connector?

There are holes & traces on the keboard to fit edge connectors for a serial ROM pack. Not a very common upgrade although the speech kit came with the connectors, the ROM packs are rare and rather useless with little/no support or software AFAIK.

Other companies like Viglen and Watford did their own ROM packs/ZIF socket upgrades which used that space.

cmorley wrote: 29 Jul 2022 10:04

Maximilian wrote: 29 Jul 2022 09:23 Wat is the use for the "ashtray" connector, is it a kind of user port connector?

There are holes & traces on the keboard to fit edge connectors for a serial ROM pack. Not a very common upgrade although the speech kit came with the connectors, the ROM packs are rare and rather useless with little/no support or software AFAIK.

Other companies like Viglen and Watford did their own ROM packs/ZIF socket upgrades which used that space.

I'm currently debating fitting a period correct (Or close to it) ZIF adapter, a new fascia (Somebody over at stardot is working on this) or simply leave as is.

A bit of finishing up with the BBC B today.

First off a bit of pimping courtesy of some nice modules from @cmorley with one of these: Solderless sideways ROM/RAM module for the Acorn BBC Model B and one of these: Solderless 64kB EEPROM module for the Acorn BBC Model B.

The 2nd module is sadly out of production, but there are still other options available over at BooBip Store.


The other ROMs are the InterWord word processor ROM and the MMFS file system ROM for the user port SD card adapter.

Now all set up on the bench with the included display stand.


The dual Cumana drive system is switchable 40/80 column, but is not hooked up or tested yet as I need to give the heads a clean and an overall service. I also need to do some proper cable management as things are getting a bit mad at the back!!

PB05 is BASIC2. Seems you have a 32KB MMFS+BASIC2 EPROM in the piggy back socket of the ROM/RAM so you could remove the BASIC mask ROM thus freeing up a socket.

My 64KB EEPROM is no longer available (chips out of production) but I replaced it with a FLASH version (64/128KB).

cmorley wrote: 07 Aug 2022 11:21 PB05 is BASIC2. Seems you have a 32KB MMFS+BASIC2 EPROM in the piggy back socket of the ROM/RAM so you could remove the BASIC mask ROM thus freeing up a socket.

I did wonder about that, thanks for the info :)

So, I pulled the lid off the Cumana 5/14 Double drive, and it's a monster!!


Despite a single power cord, there are 2 linear PSUs, one for each drive, with what looks like a rectification/filtering board in a small cage to the side. I do see electrolytics, but I'm not seeing any RIFAs so far :)

I need to give it all a bit of a clean, though I have to say, the internals, like the BBC B are very clean indeed.

Weighs a ton too!!

cmorley wrote: 07 Aug 2022 11:21 PB05 is BASIC2. Seems you have a 32KB MMFS+BASIC2 EPROM in the piggy back socket of the ROM/RAM so you could remove the BASIC mask ROM thus freeing up a socket.

My 64KB EEPROM is no longer available (chips out of production) but I replaced it with a FLASH version (64/128KB).

Ok, so I removed the basic mask ROM and I can boot to BASIC OK, as long as the MMFS/BASIC 2 rom is in the piggyback socket, otherwise it just boots to the LANGUAGE? prompt.

Also, in this config, with your adapters in any combination of slots (I tried a lot!), it works until I plug in the Interword ROM, at which point it skips basic and starts Interword on boot. If I drop the original language ROM into the 5th socket furthest away from the OS ROM, then it will boot to the BASIC prompt as expected.

I'm a bit confused as to what might be going on here, so if you have any ideas I'd be grateful. Thanks

All normal.

Your combined MMFS+BASIC ROM is a 32KB 27C256 with 2 images in - the standard sockets on a B only address 16KB hence my adapters.

The Acorn MOS checks the ROMs from 15->0. It starts the first "language" ROM it finds. Right most socket is 15 (and 3,7,11).

The "language" can use additional memory workspaces so any ROM that runs a front end is usually a "language" so word processors or PCB software etc usually have a language entry point.