Acorn Computers - Acorn Atom
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Click here for Atom programs to download
 
 
 
No serial number. The board is issue 5 with full expansion and floating point.
 
In 1979 Acorn produced boards for computer enthusiasts. The following year the company offered the Atom in kit form or ready built.
 
 
The Atom came with 2KB of RAM (expandable to 12KB) and a rather individual version of BASIC which unusually but usefully gave the ability to include machine code in a BASIC program. One oddity is the need to tell the Atom if you want a carriage return. On most computers PRINT"HELLO" followed by PRINT"GOODBYE" would place the two words on separate lines.
 
On the Atom, they appear as HELLOGOODBYE with the cursor at the end of the word. Adding PRINTCHR$13 positions the cursor at the beginning of the same line. Instead, you have to type an apostrophe ' to indicate that you want to start a new line. Failing to finish with an END instruction causes an error message.
 
The character set is upper-case letters, numbers and punctuation. In common with many computers of the time, there were no lower case letters but the SHIFT key produces letters in inverse video. Block graphics are available, but not from the keyboard. The basic Atom has only one screen resolution (mode 0) but eight others are available when fully expanded.
 
 
I've seen Atoms that start up with garbage on the screen which needs to be cleared by pressing the break key, but mine normally goes straight to the Acorn Atom prompt.
 
Despite having colour commands, output is monochrome unless a colour card is installed.
 
My Atom works well with my old portable televisions. It has an added output to AV or SCART which gives a better picture allowing me to use a wider range of televisions and monitors.
 
 
 
Rear connections. Left: Bus, VIA and printer. Right: Video out, DC in, Tape I/O, UHF output.
There are connections for a cassette recorder and a television. It could also be modified to give output to a monitor.
 
 
Ten classic games - still working!
 
The power supply at 8 volts and 1.2 amps was only sufficient for the basic computer and even then the two onboard 5 volt regulators became hot. An expanded Atom required a power supply rated at 2.5A or 3A. It was common for people to use a 5 volt psu with the Atom's regulators removed and two links installed. Having done this, the 8 volt power supply would have caused damage to the computer and could not be used.
 
A lot of software was available on ROMs. These included word processing and spreadsheets. A disk drive could be added (very expensive) and a printer interface. Banks of Atoms could be networked with a card called EcoNet.
 
 
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