--- title: Acorn Computer ATOM categories: - Computers types: - Home Computer origins: - United Kingdom years: - '1980' cpus: - '6502' params: name: ATOM company: /companies/acorn-computer company_name: Acorn Computer specs: - label: NAME value: ATOM - label: MANUFACTURER value: Acorn Computer - label: TYPE value: Home Computer - label: ORIGIN value: United Kingdom - label: YEAR value: '1980' - label: END OF PRODUCTION value: '1983' - label: BUILT IN LANGUAGE value: Basic, machine-code - label: KEYBOARD value: |- QWERTY, full-stroke keyboard, 60 keys\ ESC, BREAK, COPY, DELETE, CTRL, RETURN, LOCK, SHIFT (x2), REPT, arrow keys (x2) - label: CPU value: '6502' - label: SPEED value: 1 mHz - label: CO-PROCESSOR value: 6847 Video Display Generator, PIA 8255 (keyboard & tape) - label: RAM value: 2 KB (up to 12 KB, or 32 KB using external RAM expansion kit. ) - label: VRAM value: 6 KB - label: ROM value: 8 KB (Atom BASIC and COS), up to 16 KB - label: TEXT MODES value: 32 x 24 / 16 x 12 - label: GRAPHIC MODES value: 64 x 64 (4 colors), 64 x 96 (4 colors), 128 x 96 (monochrome), 64 x 192 (4 colors), 128 x 192 (2 colors), 256 x 192 (monochrome) - label: COLORS value: '8' - label: SOUND value: Built-in beeper - label: SIZE / WEIGHT value: 15'' long x 9.5'' deep x 2.5'' high - label: I/O PORTS value: Tape interface, UHF Modulated TV output, Acorn Bus Extension - label: POWER SUPPLY value: External PSU - 8v 2A - label: PRICE value: |- kit: £120\ Built : £170\ 50£ (UK, 1983)\ 381 (France, 82) tabs: - photos - adverts - hardware - software - emulators - links - docs photos: - title: ACORN ATOM subtitle: '' text: '' image: null - title: FRONT VIEW subtitle: '' text: '' image: null - title: SIDES subtitle: '' text: '' image: null - title: KEYBOARD CLOSE-UP subtitle: '' text: '' image: null - title: REAR CONNECTORS subtitle: '' text: The lead was a common add-on allowing to connect a composite monochrome monitor instead of using the RF modulator. image: null - title: 'MOTHERBOARD #1' subtitle: '' text: |- **(1)** Optional bus buffers. Must be installed when cards are connected to the expansion connector\ **(2)** Optional 6522 VIA chip used for the Centronics interface and hardware timers\ **(3)** 6 KB user RAM (12x2114 chips). The Atom was normally delivered with 1 KB RAM\ **(4)** Parallel Centronics connector\ **(5)** 4 KB integer BASIC ROM (top) and floating point expansion ROM (bottom)\ **(6)** 6502 CPU, here a Signetics version\ **(7)** The utility ROM socket allows a third 4 KB ROM chip to be added.\ **(8)** This motherboard version doesn't feature power regulators. Power leads are directly soldered onto the board and allow a 5V DC PSU to be connected\ **(9)** 8255 I/O chip in charge of most of the system I/O (keyboard, tape, video)\ **(10)** Motorola 6847 video controller. Manages text and graphic modes\ **(11)** 6 KB video RAM memory, also 2114 chips, only 1 KB is available in the basic version. image: null - title: 'MOTHERBOARD #2' subtitle: '' text: This version has dual built-in 5V regulators, below the aluminium heat sink, and the BBC BASIC expansion card (surrounded) image: null - title: 'MOTHERBOARD #3' subtitle: '' text: The motherboard is fixed to the case top cover. Components side faces the bottom shell. image: null - title: THE BOX subtitle: '' text: '' image: null - title: USER MANUALS subtitle: '' text: Assembly instructions and Basic language manual. image: null adverts: - title: UK ADVERT (MAY 1980) subtitle: '' text: |- Advert says: The ATOM -a definitive personal computer. Simple-to-build, simple-to-operate. But a really powerful full-facility computer. And designed on an expandable basis. You can buy a superb expanded package now-tailored to your needs. Or, you can buy just the standard Atom kit, and, as you grow in confidence and knowledge, add more chips. No need to replace your equipment. No need to worry that your investment will be overtaken by new technology. As you need more power, more facilities, you can add them! **The standard ATOM kit includes:**\ . Full sized QWERTY keyboard. Rugged polystyrene case\ . Fibreglass PCB. 2K RAM. 8K ROM. 23 integrated circuits . Full assembly instructions including tests for fault-finding. (Once built, connect it to any domestic TV and power source)\ . Power requirement: 8V at 800 M A. ATOM power unit available.\ PLUS FREE MANUAL written in two sections\ \- teach yourself BASIC and machine code for those with no knowledge of computers, and a reference section giving a complete description of the ATOM's facilities. All sections are fully illustrated with example programs. **The ATOM concept**\ Adding chips into sockets on the PCB allows you to progress in affordable steps to large-scale expansion. You can see from the specifications that the RAM can be increased to 12K allowing high resolution (256 x 192) graphics. Two further ROM chips, e.g. maths functions, can be added directly to the board giving a 16K capacity. In addition to 5 I/O lines partly used by the cassette interface, an optional VIA device can provide varied I/O and timer functions and via a buffer device allow direct printer drive. An optional module provides red, green and blue signals for colour. An in-board connector strip takes the ATOM communications loop interface. Any number of ATOMs may be tinked to each other - or to a master system with mass storage, hard copy facility. Interface with other ACORN cards is simplicity itself. Anyone ACORN card may be fitted internally. So you can see there are a vast number of modular options and additions available, expanding with your ability and your budget. **The ATOM hardware includes:**\ .Memory from 2K to 12K RAM on board (up to 35K in case)\ .8K to 16K ROM (two 4K additions) 86502 processor\ .Video Display allows high resolution (256 x 192) graphics and red, green and blue output\ .Cassette Interface-CUTS 300 baud\ .Loudspeaker allows tone generation of any frequency\ .Channel36 UHF Modulator Output .Bus output includes internal connections for Acorn Eurocard. **The ATOM software includes:**\ .32-bit arithmetic (+/- 2,000,000,000)\ .High speed execution\ .43 standard/extended BASIC commands\ .Variable length strings (up to 256 characters)\ .String manipulation functions\ .27 32-bit integer variables\ .27 additional arrays\ .random number function .PUT and GET byte\ .WAIT command for timing\ .DO-UNTIL construction\ .Logical operators (AND, OR, EX-OR)\ .LINK to machine-code routines\ .Plot draw and move. Thanks to **Paul Durrant** image: null - title: UK ADVERT (NOV. 1980) subtitle: '' text: |- Advert says: The Acorn Atom is a definitive personal computer. Simple to build, simple to operate. A powerful, full facility computer with all the features you would expect.\ Just connect the assembled computer to any domestic TV and power source and you are ready to begin. (Power requirement: 8V at 800mA). There is an ATOM power unit available. Free with every ATOM, kit or built, is a computer manual. The first section explains and teaches you BASIC, the language that most personal computers and the ATOM operate in. The instructions are simple and learning quickly becomes a pleasure. You'll soon be writing your own programs. The second section is a reference manual giving a full description of the ATOM's facilities and how to use them. Both sections arE fully illustrated with example programs. **The standard ATOM includes:**\ HARDWARE\ . Full-sized QWERTY keyboard. 6502 Microprocessor. Rugged injection-moulded case. 2K RAM. 8K HYPER-ROM\ . 23 integrated circuits and sockets. Audio cassette interface. UHF TV output. Full assembly instructions\ SOFTWARE\ . 32-bit arithmetic (:i: 2,000,000,000). High speed execution. 43 standard/extended BASIC commands. Variable length strings (up to 256 characters) . String manipulation functions. 27 x 32 bit integer variables\ . 27 additional arrays. Random number function. PUT and GET byte. WAIT command for timing. DO-UNTIL construction . Logical operators (AND, OR, EX-OR) . Link t machine - code routines. PLOT commands, DRAW and MOVE **The ATOM modular concept**\ The ATOM has been designed to grow with you. As you build confidence and knowledge you can add more components. For instance the next stage might be to increase the ROM and RAM on the basic ATOM from 8K + 2K to 12K + 12K respectively. This will give you a direct printer drive, floating point mathematics, scientific and trigonometric functions, high resolution graphics.\ From there you can expand indefinitely. Acorn have produced an enormous range of compatible PCB's which can be added to your original computer. For instance: A module to give red, green and blue colour signals Teletext VDU card (for Prestel and Ceefax information) An in-board connector for a communications loop interface - any number of ATOMs may be linked to each other or to a master system with mass storage/hard copy facility. Thanks to **Paul Durrant** image: null - title: FRENCH ADVERT subtitle: '' text: '' image: null hardware: - title: ACORN RAM/ROM CARD subtitle: '' text: This 8 KB RAM/ROM card was connected to the Atom's expansion connector. Up to 16 2114 RAM chips could be socketted, as well as 2 ROM chips, 2516 or 2532. image: null - title: 5'' 1/4 DISK-DRIVE subtitle: '' text: This disk cost about twice as much as a brand new Atom and was consequently not a big seller. The Atom disk pack was considerably larger and heavier than the computer itself. It was actually an Olivetti OPE FD 501 with 92K on a standard 5''1/4 single-sided drive. It had its own power supply - which in turn supplied power to the Atom - and used a disk operating system in ROM. image: null - title: VOLTMACE DELTA CONTROLLERS subtitle: '' text: 'Voltmace modified its Database videogame system controllers to be sold for micro-computers, mainly Acorn systems : BBC and Electron (with Plus-1 interface). As the keypad was of no use anymore, it was reduced to only 3 fire buttons.' image: /media/museum/hardware/voltmace_joysticks.jpg screenshots: - title: 3D PLOT subtitle: '' text: '' image: null - title: PLANES & TANKS BATTLE subtitle: '' text: Screenshot courtesy of Acorn Atom Emulator's home page. image: null - title: BOOT SCREEN subtitle: '' text: '' image: null - title: SNAPPER subtitle: '' text: Screenshot courtesy of Acorn Atom Emulator's home page. image: null emulators: - title: Acorn Atom Emulator url: http://www.homepages.hetnet.nl/~wouterras/atom.htm platform: MS DOS text: '' - title: The BBC Lives ! url: http://www.nvg.org/bbc/emulators.php3 platform: MS DOS text: This excellent site has a complete list of Acorn systems emulators - title: ATOMAC url: http://www.p-skids.freeserve.co.uk/#Atomac platform: Apple text: Simple ATOM emulator for Mac - title: Acorn Atom Emulator url: http://home.wxs.nl/~faase009/Ha_Atom.html platform: Unix / Linux text: '' - title: MESS emulator url: http://www.mess.org/ platform: Multiplatform text: The MESS project can emulate the Acorn links: - title: Acorn Atom Projects url: http://www.howell1964.freeserve.co.uk/Acorn/Atom/Atom.htm text: Different projects about the ATom. Quite instructive. - title: Acornusers.org url: http://www.acornusers.org/ text: The acornusers.org server hosts several Acorn web sites - title: Atom Review url: http://home.wanadoo.nl/hhaydn/ text: Nice site dedicated to the Atom - title: comp.sys.acorn.games FAQ url: http://www.landfield.com/faqs/acorn/games/ text: newsgroup FAQ - title: DOCUMENT url: http://home.wanadoo.nl/hhaydn/index-e.html text: Atom technical manual, BBC Basic, Atom layout, FDC Manual and much more - title: DOCUMENT url: http://members.aon.at/~musher/bbc/essentials.htm text: Atom user guide - title: DOCUMENT url: http://www.xs4all.nl/~fjkraan/comp/atom/atap/ text: on-line documentation, from the excellent "Oh no, not another computer museum!" - title: Oh no, not another computer museum! url: http://www.xs4all.nl/~fjkraan/comp/ text: Excellent ATOM page. - title: RetroBBC url: http://www.strafom.force9.co.uk/bbc/Retrobbc/Index.htm text: Mainly a software archive. Cool ! - title: The BBC and Master Computer Public Domain Library url: http://8bs.com/ text: Lots of stuff to see and download - title: The BBC Lives! url: http://bbc.nvg.org/ text: The net's largest site catering for enthusiasts of Acorn's range of 8-bit micros - title: The Stairway to Hell url: http://www.stairwaytohell.com/ text: Electron and BBC support. Excellent site with a lot of stuff ! - title: The Unofficial Acorn Computer User WWW Server url: http://www.poppyfields.net/acorn/ text: '' - title: Un-official ACORN ATOM Home Page url: http://www.users.globalnet.co.uk/~thoth/atom/atom.htm text: A few infos here - title: Web Wiz CAPTCHA url: http://www.webwizcaptcha.com text: Programming of Acorn computers docs: - title: ATOMIC THEORY AND PRACTICE url: https://electrickery.nl/comp/atom/atap/index.html cover: null text: |- [**ATOMIC THEORY AND PRACTICE**](https://electrickery.nl/comp/atom/atap/index.html)written by Acorn  compiled/archived by Chris Richardson / Keith Howell\  type of document : HTML\  source : [Oh no, not another computer museum!](https://electrickery.nl/comp/atom/atap/index.html) - title: ATOM TECHNICAL MANUAL url: https://electrickery.nl/comp/atom/atm/index.html cover: null text: |- [**ATOM TECHNICAL MANUAL**](https://electrickery.nl/comp/atom/atm/index.html)written by Acorn Computers Ltd  compiled/archived by Keith Howell\  type of document : HTML\  source : [Oh no, not another computer museum!](https://electrickery.nl) comments: - author: John Ferguson (UK) date: Thursday 12th April 2018 text: Owner of two Acorn Atoms one of which is for sale on Ebay at this moment. - author: Mikael (Sweden) date: Monday 14th April 2014 text: |- I have found a Emulator of Acorn Atom, and printed out an manual to. So it''s gone be nice Basic programming. I like to program Basic, but I''ll need manuals so I know how the Basic language work out. And what I can see so was Acorn Atom a good computer, the Basic is easy to understand. - author: Atom User date: Friday 1st July 2011 text: |- "A lot of applications were available on sideways ROMs that plugged into the "utility ROM socket" as Acorn called it" The ROM sockets were continuous with the address space of the 6502, so did not need page switching. The Atom supported additional ROMs but they were not ''sideways'' ROMs. - author: Roger Haycock (UK) date: Monday 4th October 2010 text: |- I built an Atom from a kit. When I switched it on I had five pictures. This was caused by dry joints in the memory. If a pin was open it was read as a one. I wrote a program to find all the dry joints and gradually I got them all fixed. I still have my Atom although some of the keys are missing. I am wondering about getting it going again. - author: DaveC (York, England) date: Tuesday 28th September 2010 text: I built my own Atom in 1979/1980. The hardest part was getting the springy key connectors through the holes in the pcb$ they kept jumping out and it took hours. The Atom was my first computer and I used it a lot while I was studying for my Electronics degree. I even used it to drive a speech synthesiser chip for my final year project. It still works! - author: AlanH date: Sunday 6th June 2010 text: |- I had a kit one that my older cousin assembled for me, although after a while it stopped working so had to send to Acorn for fixing.\ The Atom was a great little machine for the day and I cut my coding teeth on it, I must have had it for a couple of years before I could afford to buy a Beeb which was in a different league.\ After 30 yrs of programming its surprising how things haven''t really changed that much since those days on my Atom programming in BASIC and 8 bit assembler. - author: IanE (UK) date: Tuesday 9th March 2010 text: |- I had a factory built machine but a bog standard one. This came with 2K RAM. I upgraded it by buying a bag of chips which plugged into sockets pre-soldered on the board This took it up to 20K. The first one I had didn''t last long. Around the end of 1981 they converted from an external PSU to an internal one. My system came with just a length of wire that fitted in the power input socket on the back. We put a 13A plug on it and plugged it into the mains. There was a big blue flash and a bang. No more main board. My system should have had the external PSU but was supplied with just the mains cable.... they replaced it under warranty but it put a damper on Christmas Day! I kept games and programs on a reel to reel tape deck but eventually kileld the Atom by turning the output level on the tape too high. Best game was Galaxian! Just like the original including sounds but in mono and not colour. - author: a (a) date: Tuesday 30th August 2005 text: Atom is advanced for its time look @ the 3D Plot - author: Alex (Santa Cruz, CA, USA) date: Thursday 2nd October 2003 text: |- I remember building an Acorn Atom fromkit with my father (I mostly watched) I remember having to cut a yogurt container to hold the little speaker! He modded this a lot with many, many extra roms and an analog and digital joystick and a cotroller like a R/C car controller. 5 1/4 hard drive and more memory if I remember correctly. My favorite game on it was a car driving game, where your car was a line along the bottom of the screen (the hood/bonnet) and the road was just made up of little white dots that marked the side of the road. And lets not forget the lines and lines of basic code you could type in to get the magic carpet game working! related: - /museum/acorn-computer-bbc-master - /museum/acorn-computer-bbc-master-aiv - /museum/acorn-computer-bbc-master-compact - /museum/acorn-computer-bbc-model-a-b-b - /museum/acorn-computer-electron oc_id: 80 source: url: https://web.archive.org/web/20230607111542/http://www.old-computers.com/museum/computer.asp?c=80 date: '2023-06-07' --- The Acorn Atom was the ancestor of the [BBC computers series](/museum/acorn-computer-bbc-model-a-b-b/). It was sold in kit or ready-assembled versions. The great advantage of the Atom compared to its competitors ([TRS-80](/museum/tandy-radio-shack-trs-80-model-i/) & [PET](/museum/commodore-pet-2001/)), was its high resolution capabilities (256 x 192) which were quite unusual in 1979 for the price. The built-in BASIC was in some ways quite limited (it could only use integers for example) but an optional 4K ROM added the ability to use floating point numbers, trigonometric functions, to convert degrees/radians and to draw graphics in color. More add-ons were also available enabling autonumbering, a faster cassette interface (1200 bauds), and functions such as INKEY$, MID$, READ, DATA, FILL, etc... There was even a BBC BASIC board available. A lot of applications were available on sideways ROMs that plugged into the "utility ROM socket" as Acorn called it, such as the "Atom Word Pack ROM" (word processing) or Atom-Calc (a 4K ROM spreadsheet). A colour card was available, connected to the BUS connector, it provided 8 colors, 4 simultaneously at the 64 x 192 resolution or 2 at 128 x 192 for example. But it was known to overheat! A lot of other peripherals were developed : - a 5.25" floppy disk drive (100K) which held the DOS in a 3K ROM but cost about twice as much as a new Atom!,\ \- a digital-tape recorder,\ \- a printer interface,\ \- a network card called EcoNet which enabled linking of up to 250 Atoms (210 K/Bauds transfer rate),\ \- RAM expansions,\ \- etc... --- **Mr Wobbler** reports :\ The overheating of the graphics card seemed due to the conversion from NTSC to PAL. THE VC chip could be just seen under the mountain of discrete components to convert the scan rate... Programming the atom was fun, allowing the mixing of in-line assembler code embedded in basic programs. This made the transition from high level to assembler programming easier. My father bought one and had 2 subsequent replacements supplied FOC by Acorn due to problems in the video circuitry (mostly the output frequency wandering). **Peter Passchier** comments:\ The speaker was not just a beeper. You have direct write access to the I/O port, and it could be made to beep at a particular pitch by 'toggling' the speaker at a particular frequency. I used to use a one-liner that I would type in manually at night to wake me up with a warble at a desired time in the morning!