This is an upgrade in kit form which can easily give the Acorn A3000 4MB of RAM. The RAM is implemented by means of a standard 4MB 72-pin SIMM.
You will need to be able to do some basic soldering to complete the RAM board but there is no soldering needed on the A3000 motherboard itself . Pin spacing on the components is 0.1 inch and assembly is therefore definitely one of the easier projects.
The kit consists of the items in the first photo only, that is a circuit board, three 20-way connectors to match the pins by the floppy drive, two tantalum capacitors and a single 72-pin SIMM socket.
The SIMM itself is not included. Ideally a non-parity (1Mx32) SIMM would be used. The best choice is a SIMM with two 1Mx16 RAM chips, as these are the most compact. Excessively tall SIMMs with lots of components (often parity ones) can prevent the computer's lid from fitting properly.
Upgrading from 4MB to 8MB
Moving from 4MB to 8MB is not so simple - remember that this is technology from the mid 1980s and RAM was considerably more expensive.
The easy bit is to add a second 72-pin SIMM
socket to the RAM board. The holes for this are clearly visible in the photos
and soldering another socket in place is no different from the first one. You
will also require a second 4MB SIMM (you cannot use a single 8MB SIMM).
You will need to remove the 68-pin MEMC (Memory Controller) from the motherboard and put a surface mount socket in its place. This procedure is undeniably more challenging. A special 'Twin MEMC' adapter board then plugs into this socket.
Finally, the RAM board and Twin MEMC board need to be joined by a short length of bespoke 40-way ribbon cable. The cable has a conductor spacing of 0.635mm (0.025 inches) and is soldered in place at the RAM board by means of a 40-way transition connector. The connection at the Twin MEMC end is a plug/socket arrangement.
In summary, building a 4MB upgrade for the A3000 is fairly easy. Upgrading to 8MB is somewhat more involved and also relies on the availability of the MEMC chip, long since out of production.
You can find out a bit more about the Twin MEMC and 8MB upgrade for the A3000 here.