Some testing now. I'm sure you know the story so far - three different OS ROMs, but not one of them doing what I would have expected!

The ROM in my 2013 US Beeb as it arrived said it was "US MOS", but looked strikingly like the British version to me.

The US version I put in turned my machine all NTSC and was nothing like the operating system in my 1990s US Beeb.

And the German OS ROM I tried didn't work at all!

Please click on the picture links above to see more of me beginning to try to fathom it all out.

Click here to return to US BBC Model B