* CPU: 6502 1 MHz
* Co-Processor: 6847 Video Display Generator, PIA 8255 (keyboard & tape)
* RAM: 2 KB (up to 12 KB, or 32 KB using external RAM expansion kit.)
* VRAM: 6 KB
* ROM: 8 KB (Atom BASIC and COS), up to 16 KB
* Text Modes: 32 x 24 / 16 x 12
* Graphics Modes: 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)
* Colors: 8
* Sound: Built-in beeper
* I/O Ports: Tape interface, UHF Modulated TV output, Acorn Bus Extension
* Keyboard: QWERTY, full-stroke keyboard, 60 keys, ESC, BREAK, COPY, DELETE, CTRL, RETURN, LOCK, SHIFT (x2), REPT, arrow keys (x2)
* Built In Language: Basic, machine-code
MESS currently supports two different Atom configurations:
* atom [Acorn Atom]: the base version of the computer
* atomeb [Acorn Atom with Eprom Box]: the expanded version with the additional ROMs
Both drivers allows to load cassette tapes in .wav format, through the "cassette" (cass) device, and disks images in .ssd format through two floppy drives, corresponding to "floppydisk1" (flop1) and "floppydisk2" (flop2).
Also notice that a "quickload" (quik) feature is present for .atm files and that the "printer" (prin) is supported as well. Keyboard
This system requires full keyboard emulation to work correctly. At startup, full keyboard emulation mode is enabled by default. Whilst in full keyboard emulation mode, some key associated functionality may be disabled (like the ESC key for EXIT). The keyboard emulation mode is toggled using the "Scroll Lock" key (by default).
Original Keyboard: QWERTY, full-stroke keyboard, 60 keys
ESC 1! 2" 3# 4$ 5% 6& 7' 8( 9) 0 -= :* UP BREAK
RIGHT COPY Q W E R T Y U I O P @ \ DELETE
DOWN CTRL A S D F G H J K L ;+ [ ] RETURN
LOCK SHIFT Z X C V B N M ,< .> /? SHIFT REPT
The original location of the 8271 memory mapped registers is 0xa00-0x0a04. (This is the memory range assigned by Acorn in their design.) This is in the middle of the area for expansion RAM. Many Atom owners thought this was a bad design and have modified their Atom's and dos rom to use a different memory area. The atom driver in MESS uses the original memory area. (from the source)
History and Trivia
The Acorn Atom was the ancestor of the BBC computers series. It was sold in kit or ready-assembled versions.
The great advantage of the Atom compared to its competitors (TRS-80 & PET), 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.
(info from old-computers.com)
* Acorn Atom Projects -- http://www.howell1964.freeserve.co.uk/Acorn/Atom/Atom.htm
* Atom Review -- http://home.wanadoo.nl/hhaydn/index-e.html
* Atom user guide -- http://members.aon.at/~musher/bbc/essentials.htm
* Oh no, not another computer museum! -- http://www.xs4all.nl/~fjkraan/comp/
* Un-official ACORN ATOM Home Page -- http://www.users.globalnet.co.uk/~thoth/atom/atom.htm
* Acorn Atom at old-computers.com -- http://old-computers.com/museum/computer.asp?c=80
* Acorn Atom Emulator (win) -- http://www.homepages.hetnet.nl/~wouterras/atom.htm
* Acorn Atom Emulator (*nix) -- http://www.iwriteiam.nl/Ha_Atom.html
* ATOMAC (mac) -- http://www.p-skids.freeserve.co.uk/#Atomac