The Acorn Electron was a budget version of the BBC Micro educational/home computer made by Acorn Computers Ltd. It had 32 kilobytes of RAM, and its ROM memory included BBC BASIC along with its operating system.
The Electron was able to save and load programs onto audio cassette via a supplied converter cable to plug into the microphone socket of any tape recorder. It was capable of basic graphics, and could display onto either a television set or a "green screen" monitor.
At its peak, the Electron was the third best selling micro in the United Kingdom, and total lifetime game sales for the Electron exceeded those of the BBC Micro.
The hardware used on the BBC Micro was emulated by a single chip (ULA – uncommitted logic array) designed by Acorn. It had feature limitations such as being unable to output more than one channel of sound instead of being three-way polyphonic, the inability to provide teletext mode and unable to run applications from RAM as fast as the 2MHz BBC Micro, although ROM applications ran at the same speed. The ULA controlled memory access and was able to provide 32K × 8 bits of addressable RAM using 4 × 64K × 1-bit RAM chips (4164).
History
The Electron was developed during 1983 as a cheap sibling for the BBC Micro with the intention of capturing the low cost Christmas sales market for that year. Although Acorn were able to shrink substantially the same functionality as the BBC into just one custom designed ULA, manufacturing problems meant that very few machines were available for the Christmas period with some shops reporting eight presales for every delivered machine.
This was a blow from which the machine never fully recovered, although across its lifespan more games were sold for the Electron than the BBC. With hindsight, the machine was too lacking in RAM (a typical program would need to fit in only around 20kb once display memory is subtracted) and processing power to take on the prevailing ZX Spectrum and Commodore 64. Despite this, several features that would later be associated with BBC Master and Archimedes machines were first features of Electron expansion units, including the ROM cartridge slots and the Advanced Disc Filing System - a hierarchical improvement to the DFS.
Popular upgrades
A range of popular hardware upgrades were available, including the Acorn Plus 1 which added the same ROM slots later seen on the BBC Master and Plus 3 which added a double desnsity disc drive and an ADFS ROM. Support for the BBC Micro's DFS filing system was supported through use of a DFS ROM as the floppy disc hardware could function in the older single density mode.
Popular third party upgrades included the Slogger Master RAM Board which gave the system 64kb of RAM (bank switched in the low 32kb of address space, the normal ROM system remaining in the top 32kb) and various different configurations that allowed faster RAM execution speeds.
Technical information
- CPU: MOS Technology 6502A
- Clock rate: variable. CPU runs at 2 MHz when accessing ROM and 1 MHz or 0.5897 MHz (depending on graphics mode) when accessing RAM due to sharing memory access with the video display circuits. The Electron is widely misquoted as operating at 1.79 MHz after measurements derived from speed testing against the thoroughly 2 MHz BBC Micro for various pieces of 'common software'
- Coprocessor: Custom ULA
- RAM: 32 KB
- ROM: 32 KB
- Text modes: 20×32, 40×25, 40×32, 80×25, 80×32 (all text output produced by software in graphics modes)
- Graphics modes: 160×256 (4 or 16 colours), 320×256 (2 or 4 colours), 640×256 (2 colours), 320×200 (2 colours - spaced display with two blank horizontal lines following every 8 pixel lines), 640×200(2 colours - spaced display)
- Colours: 8 colours (TTL combinations of RGB primaries) + 8 flashing versions of the same colours
- Sound: 1 channel of sound, 7 octaves; built-in speaker. Software emulation of noise channel supported
- Dimensions: 16×34×6.5 cm
- I/O ports: Expansion port, tape recorder connector (1200 baud), aerial TV connector (RF modulator), RGB video monitor output
- Power supply: External PSU, 18V
Popular games
A good range of games were available for the Electron from publishers such as Acornsoft and Superior Software, notably including:
See also the list of Acorn Electron games for a fairly comprehensive list of every game published for the machine and Category:Acorn Electron games for a list of games with information on Wikipedia.
Emulation
Two emulators of the machine exist, ElectrEm ([1]) for Windows/Linux/Mac OS X and Elkulator ([2]) for Windows/DOS.
External links