Posts tagged master
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Here is one of my more recent videos – a BBC Model B playing Commodore 64 SID tunes thru the BeebSID device. There will be a new one soon about the BBC Master 512 – a 80186 PC inside a BBC Master 128.
I installed the “RetroClinic DualOS” for the BBC Master 128k today.
The DualOS Master Board from RetroClinic replaces the original 1Mbit ROM on the BBC Master 128. It contains 2 versions of the Master MOS, the original 3.20 that most machines come with, and the later MOS 3.50, with all the later versions of the utilities.
A switchable MOS gives the best of both worlds for compatibility. As was the case with the B+, and the Master when it first came out, because of changes to the OS code, software that accesses the operating system directly did not like the changes, and either ran badly, or crashed completely. This is still the case with the MOS 3.50. If you use only the later version, some of the games and utilities you used to enjoy and use will not work any more. Having both in your machine, available at the flick of a switch, gives you the most flexibility.
Both versions of the MOS have been correctly patched for the Y2K bug, so the year displays correctly from 1980 to 2079 – essential if some software was not written to be Y2K compliant, and you need to back the year off to make it run. Also, the DFS in MOS 3.50 has been patched to correct several bugs, and allow double density formatting under the DFS with the correct system calls. Add to that, the ADFSs on both versions of the operating system have been patched to use the Compact Flash Hard Drive.
You can find out more about the DualMOS at http://www.retroclinic.com/acorn/acorn.htm
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.