I have now added a fully working Acorn/BBC Master 128k and a Acorm A3020 in the collection.
The BBC Master was a home computer released by Acorn Computers in early 1986. It was designed and built for the British Broadcasting Corporation (BBC) and was the successor to the BBC Micro Model B.
The Master featured several improvements on its predecessor. The systems had 128 KB RAM as standard, alleviating the shortage of available RAM which had amongst other things discouraged use of the best graphics modes in the original design, and had two cartridge slots mounted above the new numerical keypad. Rather than the MOS Technology 6502microprocessor used by the Model B it ran on the slightly improved 65SC12 : the cost of this CPU compatibility with the Model B was that the address bus was still only 16 bits, meaning that only 64 KB could be directly addressed at any one time and the remaining memory had to be paged in as required. However the 65SC12’s extra instructions allowed a little more to be shoehorned into the OS and BBC BASIC ROMs, limited by the memory architecture to 16 KB each.