Specifications
- CPU: MOS Technology 6502
- Speed: 1 MHz
- RAM: 2 KB, expandable to 12 KB
- ROM: 8 KB, expandable to 12 KB with various Acorn and 3rd party ROMs
- Sound: 1 channel, integral loudspeaker
- Size: 381×241×64 mm
- I/O Ports: Computer Users' Tape Standard (CUTS) interface, TV connector, Centronics parallel printer
- Storage: Kansas City standard audio cassette interface
- Power: standard 2.1 mm power jack connector for 8 volts unregulated DC, providing 5 volts regulated inside the Atom
Note the Acorn 8 V power supply was only rated to 1.5 amps, which was not enough for an Atom with fully populated RAM sockets. The Atom's two internal LM7805 regulators (each regulating the + 5V for a section of the digital logic independently) also got uncomfortably hot. Therefore some Atom enthusiasts removed and by-passed the internal regulators and powered their Atoms from an external 5 V regulated power supply. Three amps were typically needed for a fully populated Atom.
There has never been a de facto standard for external 5 V connections, but using the same 7-pin DIN connectors as the Atari 800XL allowed an Atari 5V linear power supply to drive an Atom so long as the current was less than the Atari PSU rating (1 or 1.5 amps, depending on model). These are now uncommon, but 5V wall-wart switch-mode power supplies (e.g. for powering USB hubs) capable of supplying several amps are a readily and cheaply available alternative.
Read more about this topic: Acorn Atom