Acorn Electron
Encyclopedia
The Acorn Electron is a budget version of the BBC Micro
educational/home computer
made by Acorn Computers Ltd. It has 32 kilobyte
s of RAM, and its ROM
includes BBC BASIC
along with its operating system
.
The Electron was able to save and load programs onto audio cassette via a supplied converter cable that connected it to any standard tape recorder
that had the correct sockets. It was capable of basic graphics, and could display onto either a television set, a colour (RGB) monitor 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. There are at least 500 known games for the Electron and the true total is probably in the thousands.
The hardware of the BBC Micro was emulated by a single customized ULA
chip designed by Acorn. It had feature limitations such as being unable to output more than one channel of sound where the BBC was capable of three-way polyphony (plus one noise channel) and the inability to provide teletext
mode.
The ULA controlled memory access and was able to provide 32K × 8 bits of addressable RAM using 4 × 64K × 1-bit RAM
chips (4164). Due to needing two accesses to each chip instead of one, and the complications of the video hardware also needing access, reading or writing RAM was much slower than on the BBC Micro. This meant that although ROM applications ran at the same speed, there was a substantial speed decrease on applications running from RAM.
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 chip, manufacturing problems meant that very few machines were available for the Christmas period - to the extent that some shops reported eight presales for every delivered machine.
This was a blow from which the machine never fully recovered, although games sales for it would ultimately outstrip those of the BBC Micro. Following Olivetti
's 1985 cash injection into Acorn the machine was effectively sidelined.
With hindsight, the machine lacked the RAM (a typical program would need to fit in only around 20 kB once display memory is subtracted) and processing power to take on the prevailing Sinclair ZX Spectrum and Commodore 64
. Despite this, several features that would later be associated with BBC Master
and Archimedes
were first features of Electron expansion units, including ROM cartridge slots and the Advanced Disc Filing System
— a hierarchical improvement to the BBC's original Disc Filing System
.
Whilst it may not have been as popular as the Spectrum, Commodore 64 or Amstrad CPC
, it did sell in sufficient numbers to ensure that new software was being produced right up until the early 1990s. This meant the Electron had a lifespan not much shorter than those more popular micros and much longer than competitors such as the Oric-1 and Dragon 32.
Access to ROM memory occurred at 2 MHz regardless of graphics mode so theoretically programs released on ROM could run at least twice as fast as those released on tape or disc. Despite this all of the games released on ROM were packaged as 'serial ROMS', from which the micro would load programs into main memory in exactly the same way as if it were loading from tape. This meant that programs did not need to be modified for their new memory location but gave no execution speed benefits whatsoever.
drive controller and an ADFS ROM. Because the WD1770 is capable of single density mode and uses the same IBM360 derived floppy disc format as the Intel 8271 found in the BBC Micro, it was also possible to run a DFS
filing system with an alternate ROM.
The Advanced Plus 3 was very similar to the Acorn Plus 3 but packaged as a ROM cartridge for the Plus 1 with a disc drive connector at the head. This made it possible to connect a 5¼” floppy disc drive as used by BBC Micro owners or a more common 3½” drive.
The Slogger Turbo Board was a professionally fitted upgrade whereas the Elektuur modification was described in an article in Dutch Electronics magazine Elektuur and intended for users to perform at home.
Speeding up the low portion of memory is particularly useful on 6502 derived machines because that processor has a faster addressing mode for the first 256 bytes and so it is common for software to put any variables involved in time critical sections of program into that region.
If Acorn had thought to include this small modification in the original Electron design it is likely the machine would have had a much greater impact as it would have nearly doubled the amount of motion possible in games and saved modes 0–3 (including the only 16 colour mode) from being nearly useless due to contended memory timings.
Applications could not directly address video memory in this mode without modification, so it was incompatible with most games, although there is no inherent reason why a game could not be written to function in shadow mode.
During its decline, Master RAM Boards were added to every Electron in an attempt to increase sales.
The most basic solution was a pure software system supplied on a ROM cartridge that drew a low resolution approximation of the mode 7 display in a graphics mode. Although cheap and effective in enabling use of some software that only used official ROM entry points for text output, this solution proved very slow because the Electron had to be placed into an 80 byte pitch display to be able to get anywhere near to reproducing mode 7 and the CPU spent a lot of time drawing approximations of mode 7 characters and graphics that in a hardware solution would be achieved without any CPU processing. It also used up 20 kB of RAM for the graphics display rather than the 1 kB of a hardware mode 7.
Two solutions with additional hardware were provided. The first used the same graphics processor as the BBC Micro in mode 7 — the SAA5050 — but used software to ensure that it was fed with the correct graphics data. A software ROM would put the machine into an ordinary 40 byte pitch display. While the ULA would read the display from memory in the usual fashion, the SAA5050 would listen to the data it was reading and produce a mode 7 interpretation of the same information. When necessary the hardware would switch between the graphics output being produced by the micro and that being produced by the add-on.
The disadvantage to this system is that while the SAA5050 would expect to be repeatedly fed the same 40 bytes of data for every display scanline of every character row, the ULA would read a different set of 40 bytes for every display scanline in order to produce a full graphics display. A software ROM worked around this by duplicating the data intended for a mode 7 display in memory. Although this produced a mode 7 that barely impacted upon CPU performance and gave the same visual quality as the BBC Micro, it remained compatible only with software that used the ROM routines for outputting text and graphics and still used 10 kB of memory for the display.
A second version of the hardware add-on corrected these problems. By adding a CRTC6845 to the package, a full hardware solution was created that did not reduce CPU performance and only used 1 kB of memory for the display. A software ROM was still supplied, but this did no more than expand the hardware ROM so that it knew mode 7 now existed and was able to switch into it.
. The ROM firmware provided dial-up communications facilities. These were used by the Interflora
florists network in the UK for over a decade.
Like the BBC Micro
, the Electron was constrained by limited memory resources. Of the 32 KB RAM, 3½ KB was allocated to the OS at startup and at least 10 KB was taken up by the display buffer in contiguous display modes.
Due to the timing of interrupts it was possible to disable either the top 100 or bottom 156 lines of the display with palette changes. Many games took advantage of this, gaining storage by leaving non-graphical data in the disabled area.
Other games would load non-graphical data into the display, leaving it visible as regions of apparently randomly coloured pixels.
Although page flipping was a hardware possibility, the limited memory forced most applications to do all their drawing directly to the visible screen, often resulting in graphical flicker
or visible redraw. A notable exception is Players' Joe Blade
series.
FireTrack
exploits a division in the way the Electron handles its display — of the seven available graphics modes, two are configured so that the final two of every ten scanlines are blank and are not based on the contents of RAM. If 16 scanlines of continuous graphical data are written to a character-block-aligned portion of the screen then they will appear as a continuous block in most modes but in the two non-continuous modes they will be displayed as two blocks of 8 scanlines, separated in the middle by two blank scanlines.
In order to keep track of its position within the display, the Electron maintains an internal display address counter. The same counter is used in both the continuous and non-continuous graphics modes and switching modes mid-frame does not cause any adjustment to the counter.
FireTrack switches from a non-continuous to a continuous graphics mode part way down the display. By using the palette to mask the top area of the display and taking care about when it changes mode it can shift the continuous graphics at the bottom of the display down in two pixel increments because the internal display counter is not incremented on blank scanlines during non-continuous graphics modes.
output.
The speaker can be programmatically switched on or off at any time but is permanently attached to a hardware counter so is normally only able to output a square wave. But if set to a frequency outside the human audible range then the ear can't perceive the square wave, only the difference between the speaker being switched on and off. This gives the effect of a simple toggle speaker similar to that seen in the 48 kB Sinclair ZX Spectrum. Exile uses this to output 1-bit audio samples.
and Sinclair ZX Spectrum, a good range of games were available for the Electron. The traditional BBC Micro
publishers such as Acornsoft
, Superior Software
and Micro Power
offered the widest support. Notable popular games particularly associated with the Electron include:
There were also many popular games officially converted to the Electron from arcade machines (including Crystal Castles, Tempest, Commando
, Paperboy
and Yie Ar Kung-Fu) or other home computer systems (including Impossible Mission
, Jet Set Willy
, The Way of the Exploding Fist
, Tetris
, The Last Ninja
, Barbarian
and SimCity
).
Despite Acorn themselves effectively shelving the Electron in 1985, games continued to be developed and released by professional software houses until 1991. There were around 1,400 games released for the Acorn Electron, several thousand extra public domain titles were released on disc through Public Domain libraries. Notable enterprises which produced discs of such software are BBC PD, Electron User Group and HeadFirst PD
.
See also the list of Acorn Electron games for a fairly comprehensive list of games published for the machine and :Category:BBC Micro and Acorn Electron games for a list of games with information on Wikipedia.
/Linux
/Mac OS X
, Elkulator (http://elkulator.acornelectron.co.uk) for Windows
/DOS
and the Multi-system emulator MESS
. Electron software is predominantly archived in the UEF
file format
.
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
educational/home computer
Home computer
Home computers were a class of microcomputers entering the market in 1977, and becoming increasingly common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user...
made by Acorn Computers Ltd. It has 32 kilobyte
Kilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
s of RAM, and its ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
includes BBC BASIC
BBC BASIC
BBC BASIC is a programming language, developed in 1981 as a native programming language for the MOS Technology 6502 based Acorn BBC Micro home/personal computer, mainly by Sophie Wilson. It is a version of the BASIC programming language adapted for a U.K...
along with its operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
.
The Electron was able to save and load programs onto audio cassette via a supplied converter cable that connected it to any standard tape recorder
Tape recorder
An audio tape recorder, tape deck, reel-to-reel tape deck, cassette deck or tape machine is an audio storage device that records and plays back sounds, including articulated voices, usually using magnetic tape, either wound on a reel or in a cassette, for storage...
that had the correct sockets. It was capable of basic graphics, and could display onto either a television set, a colour (RGB) monitor or a "green screen" monitor.
At its peak, the Electron was the third best selling micro in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, and total lifetime game sales for the Electron exceeded those of the BBC Micro. There are at least 500 known games for the Electron and the true total is probably in the thousands.
The hardware of the BBC Micro was emulated by a single customized ULA
Gate array
A gate array or uncommitted logic array is an approach to the design and manufacture of application-specific integrated circuits...
chip designed by Acorn. It had feature limitations such as being unable to output more than one channel of sound where the BBC was capable of three-way polyphony (plus one noise channel) and the inability to provide teletext
Teletext
Teletext is a television information retrieval service developed in the United Kingdom in the early 1970s. It offers a range of text-based information, typically including national, international and sporting news, weather and TV schedules...
mode.
The ULA controlled memory access and was able to provide 32K × 8 bits of addressable RAM using 4 × 64K × 1-bit RAM
Random-access memory
Random access memory is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order with a worst case performance of constant time. Strictly speaking, modern types of DRAM are therefore not random access, as data is read in...
chips (4164). Due to needing two accesses to each chip instead of one, and the complications of the video hardware also needing access, reading or writing RAM was much slower than on the BBC Micro. This meant that although ROM applications ran at the same speed, there was a substantial speed decrease on applications running from RAM.
History
The Electron was developed during 1983 as a cheap sibling for the BBC MicroBBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
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
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
into just one chip, manufacturing problems meant that very few machines were available for the Christmas period - to the extent that some shops reported eight presales for every delivered machine.
This was a blow from which the machine never fully recovered, although games sales for it would ultimately outstrip those of the BBC Micro. Following Olivetti
Olivetti
Olivetti S.p.A. is an Italian manufacturer of computers, printers and other business machines.- Founding :The company was founded as a typewriter manufacturer in 1908 in Ivrea, near Turin, by Camillo Olivetti. The firm was mainly developed by his son Adriano Olivetti...
's 1985 cash injection into Acorn the machine was effectively sidelined.
With hindsight, the machine lacked the RAM (a typical program would need to fit in only around 20 kB once display memory is subtracted) and processing power to take on the prevailing Sinclair ZX Spectrum and Commodore 64
Commodore 64
The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595...
. Despite this, several features that would later be associated with BBC Master
BBC Master
The BBC Master was a home computer released by Acorn Computers in early 1986. It was designed and built for the British Broadcasting Corporation and was the successor to the BBC Micro Model B. The Master 128 remained in production until 1993....
and Archimedes
Acorn Archimedes
The Acorn Archimedes was Acorn Computers Ltd's first general purpose home computer to be based on their own ARM architecture.Using a RISC design with a 32-bit CPU, at its launch in June 1987, the Archimedes was stated as running at 4 MIPS, with a claim of 18 MIPS during tests.The name is commonly...
were first features of Electron expansion units, including ROM cartridge slots and the Advanced Disc Filing System
Advanced Disc Filing System
The Advanced Disc Filing System is a computing file system particular to the Acorn computer range and RISC OS based successors. Initially based on the rare Acorn Winchester Filing System, it was renamed to the Advanced Disc Filing System when support for floppy discs was added and on later 32 bit...
— a hierarchical improvement to the BBC's original Disc Filing System
Disc Filing System
The Disc Filing System is a computer file system developed by Acorn Computers Ltd, and introduced in 1982 for the Acorn BBC Microcomputer. It was shipped as a ROM to be inserted onto the BBC Micro's motherboard. It has an extremely limited design, and uses a flat directory structure...
.
Whilst it may not have been as popular as the Spectrum, Commodore 64 or Amstrad CPC
Amstrad CPC
The Amstrad CPC is a series of 8-bit home computers produced by Amstrad between 1984 and 1990. It was designed to compete in the mid-1980s home computer market dominated by the Commodore 64 and the Sinclair ZX Spectrum, where it successfully established itself primarily in the United Kingdom,...
, it did sell in sufficient numbers to ensure that new software was being produced right up until the early 1990s. This meant the Electron had a lifespan not much shorter than those more popular micros and much longer than competitors such as the Oric-1 and Dragon 32.
Acorn Plus 1
The Acorn Plus 1 added two ROM slots, an analogue interface and a parallel port. The analogue interface was normally used for joysticks, the parallel for a printer.Access to ROM memory occurred at 2 MHz regardless of graphics mode so theoretically programs released on ROM could run at least twice as fast as those released on tape or disc. Despite this all of the games released on ROM were packaged as 'serial ROMS', from which the micro would load programs into main memory in exactly the same way as if it were loading from tape. This meant that programs did not need to be modified for their new memory location but gave no execution speed benefits whatsoever.
Acorn Plus 3
The Acorn Plus 3 was a hardware module that connected independently of the Plus 1 and provided a double-density 3½” disc drive connected through a WD1770WD1770
The FD1771 is the first in a line of floppy disk controllers produced by Western Digital. It uses single density modulation and supports the IBM 3740 disk format...
drive controller and an ADFS ROM. Because the WD1770 is capable of single density mode and uses the same IBM360 derived floppy disc format as the Intel 8271 found in the BBC Micro, it was also possible to run a DFS
Disc Filing System
The Disc Filing System is a computer file system developed by Acorn Computers Ltd, and introduced in 1982 for the Acorn BBC Microcomputer. It was shipped as a ROM to be inserted onto the BBC Micro's motherboard. It has an extremely limited design, and uses a flat directory structure...
filing system with an alternate ROM.
First Byte Joystick Interface
As a games machine the Electron shared the same failing as the Sinclair Spectrum in not having a joystick port. This was quickly remedied by First Byte Computers who developed an interface and software which allowed a "switched" joystick to be used with the majority of software titles. This interface became very popular and was sold by W.H. Smiths, Boots, Comet and hundreds of independent computer dealers.P.R.E.S. Advanced Plus 3
Slogger/Elektuur Turbo Board
The Slogger and Elektuur Turbo Boards were born out of a hack initially devised at Acorn. By moving the lowest 8 KB of RAM outside of reach of the ULA, the CPU could always access it at 2 MHz. The tradeoff was that the screen could not be located in that 8 KB. In practice the operating system ROMs always put the screen into the top 24 KB and as a result this probably only broke compatibility with around 2% of software.The Slogger Turbo Board was a professionally fitted upgrade whereas the Elektuur modification was described in an article in Dutch Electronics magazine Elektuur and intended for users to perform at home.
Speeding up the low portion of memory is particularly useful on 6502 derived machines because that processor has a faster addressing mode for the first 256 bytes and so it is common for software to put any variables involved in time critical sections of program into that region.
If Acorn had thought to include this small modification in the original Electron design it is likely the machine would have had a much greater impact as it would have nearly doubled the amount of motion possible in games and saved modes 0–3 (including the only 16 colour mode) from being nearly useless due to contended memory timings.
Slogger Master RAM Board
A development of the Turbo Board, the Master RAM Board duplicated the Turbo Board functionality and added a further option of running the micro with 32 kB of shadow RAM in addition to the ordinary 32 kB — giving 64 kB total. Some clever program counter catches meant that the ordinary system ROMs and any software using the OS calls could function without significant modification, making substantially more memory available for BASIC, View, Viewsheet and almost every other business application. By providing extra storage this modification also allowed some games and applications intended for the BBC Micro to function on the Electron despite the lack of a native Mode 7.Applications could not directly address video memory in this mode without modification, so it was incompatible with most games, although there is no inherent reason why a game could not be written to function in shadow mode.
During its decline, Master RAM Boards were added to every Electron in an attempt to increase sales.
Jafa Systems Mode 7 Display Unit
Of the capabilities present in the BBC Micro but absent from the Electron, the teletext style mode 7 was particularly conspicuous because of the very low memory usage in that mode (just less than 1 kB) and the high number of BBC programs that used it. Jafa Systems provided a number of solutions to redress this deficiency.The most basic solution was a pure software system supplied on a ROM cartridge that drew a low resolution approximation of the mode 7 display in a graphics mode. Although cheap and effective in enabling use of some software that only used official ROM entry points for text output, this solution proved very slow because the Electron had to be placed into an 80 byte pitch display to be able to get anywhere near to reproducing mode 7 and the CPU spent a lot of time drawing approximations of mode 7 characters and graphics that in a hardware solution would be achieved without any CPU processing. It also used up 20 kB of RAM for the graphics display rather than the 1 kB of a hardware mode 7.
Two solutions with additional hardware were provided. The first used the same graphics processor as the BBC Micro in mode 7 — the SAA5050 — but used software to ensure that it was fed with the correct graphics data. A software ROM would put the machine into an ordinary 40 byte pitch display. While the ULA would read the display from memory in the usual fashion, the SAA5050 would listen to the data it was reading and produce a mode 7 interpretation of the same information. When necessary the hardware would switch between the graphics output being produced by the micro and that being produced by the add-on.
The disadvantage to this system is that while the SAA5050 would expect to be repeatedly fed the same 40 bytes of data for every display scanline of every character row, the ULA would read a different set of 40 bytes for every display scanline in order to produce a full graphics display. A software ROM worked around this by duplicating the data intended for a mode 7 display in memory. Although this produced a mode 7 that barely impacted upon CPU performance and gave the same visual quality as the BBC Micro, it remained compatible only with software that used the ROM routines for outputting text and graphics and still used 10 kB of memory for the display.
A second version of the hardware add-on corrected these problems. By adding a CRTC6845 to the package, a full hardware solution was created that did not reduce CPU performance and only used 1 kB of memory for the display. A software ROM was still supplied, but this did no more than expand the hardware ROM so that it knew mode 7 now existed and was able to switch into it.
Merlin M2105
An unusual variant of the Electron was sold by British Telecom Business Systems as the BT Merlin M2105 Communications Terminal. This consisted of a de-badged Electron plus a large expansion unit containing 32 KB of RAM, 48 KB of ROM, a Centronics printer port and a modemModem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...
. The ROM firmware provided dial-up communications facilities. These were used by the Interflora
Interflora
Interflora is the most commonly used name for a group of organisations worldwide, providing florists with a brand under which flowers can be purchased and delivered to 140 countries, most with their own partnership, or unit.- History :...
florists network in the UK for over a decade.
Hardware
- CPUCentral processing unitThe central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
: MOS TechnologyMOS TechnologyMOS Technology, Inc., also known as CSG , was a semiconductor design and fabrication company based in Norristown, Pennsylvania, in the United States. It is most famous for its 6502 microprocessor, and various designs for Commodore International's range of home computers.-History:MOS Technology, Inc...
6502AMOS Technology 6502The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of... - 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: Ferranti SemiconductorFerrantiFerranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. Known primarily for defence electronics, the Company was once a constituent of the FTSE 100 Index but ceased trading in 1993.The...
Custom ULAGate arrayA gate array or uncommitted logic array is an approach to the design and manufacture of application-specific integrated circuits... - RAMRandom-access memoryRandom access memory is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order with a worst case performance of constant time. Strictly speaking, modern types of DRAM are therefore not random access, as data is read in...
: 32 kBKilobyteThe kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information... - ROMRead-only memoryRead-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
: 32 kBKilobyteThe kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information... - 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 baudBaudIn telecommunications and electronics, baud is synonymous to symbols per second or pulses per second. It is the unit of symbol rate, also known as baud rate or modulation rate; the number of distinct symbol changes made to the transmission medium per second in a digitally modulated signal or a...
variation on the Kansas City standardKansas City standardThe Kansas City Standard , or Byte standard, is a digital data format for audio cassette drives. Byte magazine sponsored a symposium in November 1975 in Kansas City, Missouri to develop a standard for storage of digital computer data on inexpensive consumer quality cassettes, at a time when...
for data encoding), aerial TV connector (RF modulatorRF modulatorAn RF modulator is a device that takes a baseband input signal and outputs a radio frequency-modulated signal....
), composite videoComposite videoComposite video is the format of an analog television signal before it is combined with a sound signal and modulated onto an RF carrier. In contrast to component video it contains all required video information, including colors in a single line-level signal...
and RGB monitor output - Power supply: External PSU, 18VVoltThe volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
ACAlternating currentIn alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
Quirks
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
, the Electron was constrained by limited memory resources. Of the 32 KB RAM, 3½ KB was allocated to the OS at startup and at least 10 KB was taken up by the display buffer in contiguous display modes.
Due to the timing of interrupts it was possible to disable either the top 100 or bottom 156 lines of the display with palette changes. Many games took advantage of this, gaining storage by leaving non-graphical data in the disabled area.
Other games would load non-graphical data into the display, leaving it visible as regions of apparently randomly coloured pixels.
Although page flipping was a hardware possibility, the limited memory forced most applications to do all their drawing directly to the visible screen, often resulting in graphical flicker
Flicker (screen)
Flicker is a visible fading between cycles displayed on video displays, especially the refresh interval on cathode ray tube based computer screens. Flicker occurs on CRTs when they are driven at a low refresh rate, allowing the brightness to drop for time intervals sufficiently long to be noticed...
or visible redraw. A notable exception is Players' Joe Blade
Joe Blade
Joe Blade is the title of a series of budget-price platform games written by Colin Swinbourne and published by Players.All three titles were flick-screen adventures, in which the player controls the titular character through a number of rooms, dispatching enemies and rescuing innocent people...
series.
FireTrack: smooth vertical scrolling
Although programs can alter the position of the screen in memory, the non-linear format of the display means that vertical scrolling can only be done in blocks of 8 pixels without further work.FireTrack
Firetrack
Firetrack is a vertically-scrolling shoot 'em up computer game programmed by Nick "Orlando" Pelling and released for the BBC Micro and Commodore 64 platforms in 1987 by Electric Dreams Software. It was also ported to the Acorn Electron by Superior Software in 1989 as part of the Play It Again Sam 7...
exploits a division in the way the Electron handles its display — of the seven available graphics modes, two are configured so that the final two of every ten scanlines are blank and are not based on the contents of RAM. If 16 scanlines of continuous graphical data are written to a character-block-aligned portion of the screen then they will appear as a continuous block in most modes but in the two non-continuous modes they will be displayed as two blocks of 8 scanlines, separated in the middle by two blank scanlines.
In order to keep track of its position within the display, the Electron maintains an internal display address counter. The same counter is used in both the continuous and non-continuous graphics modes and switching modes mid-frame does not cause any adjustment to the counter.
FireTrack switches from a non-continuous to a continuous graphics mode part way down the display. By using the palette to mask the top area of the display and taking care about when it changes mode it can shift the continuous graphics at the bottom of the display down in two pixel increments because the internal display counter is not incremented on blank scanlines during non-continuous graphics modes.
Exile: sampled speech
Exile turns the Electron's one channel output into a digital speaker for PCMPulse-code modulation
Pulse-code modulation is a method used to digitally represent sampled analog signals. It is the standard form for digital audio in computers and various Blu-ray, Compact Disc and DVD formats, as well as other uses such as digital telephone systems...
output.
The speaker can be programmatically switched on or off at any time but is permanently attached to a hardware counter so is normally only able to output a square wave. But if set to a frequency outside the human audible range then the ear can't perceive the square wave, only the difference between the speaker being switched on and off. This gives the effect of a simple toggle speaker similar to that seen in the 48 kB Sinclair ZX Spectrum. Exile uses this to output 1-bit audio samples.
Popular games
Although not as well supported by the biggest software publishers as rivals like the Commodore 64Commodore 64
The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595...
and Sinclair ZX Spectrum, a good range of games were available for the Electron. The traditional BBC Micro
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
publishers such as Acornsoft
Acornsoft
Acornsoft was the software arm of Acorn Computers Ltd, and a major publisher of software for the BBC Micro and Acorn Electron. As well as games, they also produced a large number of educational titles, extra computer languages and business and utility packages - these included ROM-based word...
, Superior Software
Superior Software
Superior Software is a video game publisher. It was established in 1982 by Richard Hanson and John Dyson, two graduates of the University of Leeds, England...
and Micro Power
Micro Power
Micro Power was a British company established in the early 1980s, best known as a video game publisher but they also produced and sold many types of computer hardware and software through their Leeds...
offered the widest support. Notable popular games particularly associated with the Electron include:
- Starship CommandStarship CommandAcornsoft's Starship Command is a computer game released in 1983 for the BBC Micro and Acorn Electron. It was available on cassette as well as 5.25" disc for the BBC and ROM cartridge for the Acorn Electron Plus 1 expansion module.-Gameplay:...
(AcornsoftAcornsoftAcornsoft was the software arm of Acorn Computers Ltd, and a major publisher of software for the BBC Micro and Acorn Electron. As well as games, they also produced a large number of educational titles, extra computer languages and business and utility packages - these included ROM-based word...
, 1983) - Chuckie EggChuckie EggA&F Software's Chuckie Egg is a home computer video game released in 1983, initially for the ZX Spectrum, the BBC Micro and the Dragon. Its subsequent popularity saw it released over the following years on a wide variety of computers, including the Commodore 64, Acorn Electron, MSX, Tatung...
(A'n'F, 1984) - Elite (AcornsoftAcornsoftAcornsoft was the software arm of Acorn Computers Ltd, and a major publisher of software for the BBC Micro and Acorn Electron. As well as games, they also produced a large number of educational titles, extra computer languages and business and utility packages - these included ROM-based word...
, 1984) - the Repton series (Superior SoftwareSuperior SoftwareSuperior Software is a video game publisher. It was established in 1982 by Richard Hanson and John Dyson, two graduates of the University of Leeds, England...
, 1985–1989) - Thrust (Superior SoftwareSuperior SoftwareSuperior Software is a video game publisher. It was established in 1982 by Richard Hanson and John Dyson, two graduates of the University of Leeds, England...
, 1986) - Exile (Superior SoftwareSuperior SoftwareSuperior Software is a video game publisher. It was established in 1982 by Richard Hanson and John Dyson, two graduates of the University of Leeds, England...
, 1988)
There were also many popular games officially converted to the Electron from arcade machines (including Crystal Castles, Tempest, Commando
Commando (arcade game)
is a vertically scrolling shoot 'em up arcade game released in 1985. Its influence can be seen in several later games in the genre ....
, Paperboy
Paperboy (video game)
Paperboy is a 1984 arcade game by Atari Games. The players take the role of a paperboy who delivers newspapers along a suburban street on his bicycle. This game was innovative for its theme and novel controls.-Gameplay:...
and Yie Ar Kung-Fu) or other home computer systems (including Impossible Mission
Impossible Mission
Impossible Mission is a platform computer game for several home computers. The original version for the Commodore 64 was programmed by Dennis Caswell and published by Epyx in 1984.-Description:...
, Jet Set Willy
Jet Set Willy
Jet Set Willy is a computer game originally written for the ZX Spectrum home computer. It was published in 1984 by Software Projects and ported to most home computers of the time....
, The Way of the Exploding Fist
The Way of the Exploding Fist
The Way of the Exploding Fist is a 1985 fighting game by Gregg Barnett of Beam Software. Originally developed on the Commodore 64 and published in June 1985 by Melbourne House, ports were made for Amstrad CPC, ZX Spectrum, BBC Micro, Acorn Electron and Commodore 16...
, Tetris
Tetris
Tetris is a puzzle video game originally designed and programmed by Alexey Pajitnov in the Soviet Union. It was released on June 6, 1984, while he was working for the Dorodnicyn Computing Centre of the Academy of Science of the USSR in Moscow, Russian Soviet Federative Socialist Republic...
, The Last Ninja
The Last Ninja
The Last Ninja is an action-adventure game developed and published by System 3 in 1987 for the Commodore 64. As the first in the Last Ninja series, it set the standard for the unique look and feel for its sequels: Last Ninja 2 , Last Ninja Remix and Last Ninja 3...
, Barbarian
Barbarian (computer game)
Barbarian: The Ultimate Warrior is a video game first released for Commodore 64 personal computers in 1987; the title was developed and published by Palace Software, and ported to other computers in the following months. The developers licensed the game to Epyx, who published it as Death Sword in...
and SimCity
SimCity
SimCity is a critically acclaimed city-building simulation video game, first released in 1989, and designed by Will Wright. SimCity was Maxis' first product, which has since been ported into various personal computers and game consoles, and spawned several sequels including SimCity 2000 in 1994,...
).
Despite Acorn themselves effectively shelving the Electron in 1985, games continued to be developed and released by professional software houses until 1991. There were around 1,400 games released for the Acorn Electron, several thousand extra public domain titles were released on disc through Public Domain libraries. Notable enterprises which produced discs of such software are BBC PD, Electron User Group and HeadFirst PD
HeadFirst PD
HeadFirst Public Domain was a library of public domain software for the BBC Micro and Acorn Electron 8-bit computers. It also offered several discs of software for the Acorn Archimedes....
.
See also the list of Acorn Electron games for a fairly comprehensive list of games published for the machine and :Category:BBC Micro and Acorn Electron games for a list of games with information on Wikipedia.
Emulation
Three emulators of the machine exist, ElectrEm (http://electrem.emuunlim.com) for WindowsMicrosoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
/Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
/Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
, Elkulator (http://elkulator.acornelectron.co.uk) for Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
/DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...
and the Multi-system emulator MESS
MESS
Multi Emulator Super System is an emulator for many game consoles and computer systems, based on the MAME core.The primary purpose of MESS is to preserve decades of computer and console history...
. Electron software is predominantly archived in the UEF
UEF (file format)
Unified Emulator Format is a container format for the compressed storage of audio tapes, ROMs, floppy disks and machine state snapshots for the 8-bit range of computers manufactured by Acorn Computers...
file format
File format
A file format is a particular way that information is encoded for storage in a computer file.Since a disk drive, or indeed any computer storage, can store only bits, the computer must have some way of converting information to 0s and 1s and vice-versa. There are different kinds of formats for...
.