Here I have unscrewed the Atom PCB from the lid and turned it over whilst resting on the upturned lid to stop the PCB scratching the table.

All the components, then, are on the underside of the PCB. There is only one circuit board inside the Atom, amalgamating the keyboard and computer circuitry in one.

When new, the Atom could be bought either as a ready made computer or as a kit. If you bought the kit, you had to solder all the components onto the circuit board yourself.

I am very lucky to have a full upgraded Atom. You can see that all the IC sockets are filled.

At its basic level, the Atom had 2K RAM and a combined Operating System/BASIC ROM.

It could be upgraded to 12K, split between text RAM and video RAM.

A 6522 VIA could be added, as well as the Acorn Bus Extension interface and a printer interface. There are two ROM sockets for user ROM expansion.

My Atom has all these upgrades installed.

I am not sure what the two ROMs are. One of them (IC 21) I cannot read but the chip in IC 24 reads "Atom M/C ROM 1.1 Micrologic"

The only two other internal upgrades to the Atom that I know of were the Atom Colour Card and the Atom Econet Card.

By using the Acorn Expansion Bus, the Atom could be upgraded to BBC BASIC and a disc filing system amongst other things.