{"id":2048,"date":"2025-05-04T18:51:05","date_gmt":"2025-05-04T18:51:05","guid":{"rendered":"https:\/\/vintage.bohemiancave.org.uk\/?p=2048"},"modified":"2025-12-22T03:15:34","modified_gmt":"2025-12-22T03:15:34","slug":"bbc-master-128","status":"publish","type":"post","link":"https:\/\/vintage.bohemiancave.org.uk\/index.php\/bbc-master-128\/","title":{"rendered":"BBC Master 128"},"content":{"rendered":"\n
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After Acorn’s success with the BBC Microcomputer, they took all the add-on’s that had been made for it, added some finesse of their own and created the BBC Master. It’s mostly backward compatible with the earlier computer… but not quite.<\/p>\n<\/div>\n<\/div>\n\n\n\n

Hardware<\/h2>\n\n\n\n

The BBC Master computer came in many flavours: the Master 128 was the base model that all others were based on. The 128 in the name refers to the total RAM that the machine was imbued with.<\/p>\n\n\n\n

The other models were the 512 (PC Compatible), AIV (Advanced Interactive Videodisc), ET (Econet Terminal), Scientific, and the Master Compact and Olivetti Prodest PC 128. The latter two were essentially the same machine, with a different motherboard (with fewer interfaces), and a cheaper keyboard design. The ET had the same motherboard as the 128 but with many components missing and an Econet interface as standard. You can read more about the different versions on Wikipedia<\/a>.<\/p>\n\n\n\n

The RAM in the Master is laid out like in the BBC Micro<\/a> with some additions. Like the Model B it has 32K of main memory, and in addition it has four banks of 16K sideways RAM, 20K of shadow RAM (to optionally be used for the screen), 8K of workspace RAM (mostly for filesystems) and 4K OS workspace RAM. This extra RAM allows programs to use considerably more of the systems main memory, not having to share it with the display or the filesystems.<\/p>\n\n\n\n

The CPU in the Master is a bump up from that in the Model B – it’s a 65SC12 rather than a 6502A. They are both clocked at 2MHz but the Master’s CPU is considerably more efficient.<\/p>\n\n\n\n

An interesting addition is that of Real Time Clock and battery-backed settings. The clock could be added to the BBC Micro<\/a> (intended for use in an econet fileserver), plugged into the user port. The addon is extremely rare.<\/p>\n\n\n\n

The Master contains a built-in 1772 disc interface controller, a step up from the Model Bs original 8271 and later 1770. The DFS filesystem was standard on the Model B, but with the 1770 disk controller ADFS can be used as an alternative (or in conjunction with it). The Master uses the better ADFS by default but also has DFS built-in. Each filing system on the computer requires workspace, ADFS requires more than DFS. On the Model B this space is taken from the main system RAM, reducing the amount left available for program use. On the Master, however, this is not the case as there is workspace reserved for this use.<\/p>\n\n\n\n

Filesystems, utility programs and languages on the BBC Micro and Master reside in sideways ROM (or RAM). This is a fixed area of 16K of memory, bank switched to any one of sixteen images. Originally, such images always came as ROMs on the Model B although sideways RAM became a common add-on to the machine to allow utilities and different languages to be installed from disc. This addition has been carried through to the Master in the form of four banks of sideways RAM.<\/p>\n\n\n\n

The TUBE interface on the Model B has been retained, but also enhanced by means of an internal TUBE interface. The battery-backed settings hold the on or off state and which of the internal or external TUBE interfaces is in use.<\/p>\n\n\n\n

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All the external interfaces – RS423 serial, parallel printer, 1MHz bus, user port, tape, analogue, RGB and composite video are exactly the same as on the Model B. In addition, there are are two cartridge ports on the Master. By default they can hold two ROM images each although certain other control lines, like IRQ and NMI are passed to the cartridge ports. There is also audio in and out. One port can even have certain signals routed to it, through an internal link, enabling the use of genlock hardware. More detail is provided on Chris’ Acorns<\/a>.<\/p>\n<\/div>\n<\/div>\n\n\n\n

Econet was introduced by Acorn as a proprietary networking system for their machines. At the time it was considerably cheaper than Ethernet and was extremely capable. Many schools adopted it. On the Model B, econet had to be installed by soldering components to the motherboard. On the Master, however, ethernet was installed by simply installing an add-in card. That same card was used in their Archimedes computers too. Econet networks require a 5-pin din cable to connect machines to a junction box and many junction boxes were linked together. In the middle of a line of these was a clock box. Networks could also be bridged. The econet network allowed many stations (BBC machines) to share resources on a file or print server. Econet was also capable of much more.<\/p>\n\n\n\n

Summary<\/h3>\n\n\n\n