Raspberry Pi Compute Module explained

You can now get the Raspberry Pi as a stick – but what exactly is the Compute Module?

I like the Raspberry Pi website’s new redesign! It’s very nice. I went there to have a look at it and they’d announced a new Raspberry Pi. Is it a new Raspberry Pi model? It looked like a stick.

That would be the Raspberry Pi Compute Module. And no, the Compute Module version of the Raspberry Pi is not a new Raspberry Pi model or the oft-rumoured Raspberry Pi Model C.

Is it a Raspberry Pi 2 then?

Also no, it’s just a radically different form factor of the Raspberry Pi with the same chips and such as the original version.

The computer module looks like a stick of SODIMM RAM
The computer module looks like a stick of SODIMM RAM

Wait, there’s a ‘rumoured’ Model C Raspberry Pi? What would that be?

Well there are currently two models of Raspberry Pi, ignoring the computer module. The Model A and Model B are basically the same, albeit with slightly different hardware configurations. The Model A only has one USB port and no Ethernet, whereas the Model B as two USB ports, the Ethernet port and more RAM. The Model C is a predicted version of the Raspberry Pi that adds Wi-Fi. It’s purely speculation though, as there’s no real evidence anywhere to suggest this is happening.

Right, so it’s not a new model. Why is it called the Compute Module then?

It’s literally just the computational chips that come on the Raspberry Pi along with some flash memory to replace the SD card. It can do the same work as a Raspberry Pi would as it has the same chips and can therefore run the same software.

What does it offer over a normal Raspberry Pi, then?

It’s mainly the smaller form-factor, with the bonus of being a little bit cheaper than a full Raspberry Pi.

One thing I’ve noticed is that it doesn’t seem to have any of the normal inputs and outputs. Neither does it have a power connector. How do you use it?

The connectors on one side of the module are the same size as a DDR2 SODIMM, a standard that’s used for laptop and mini-PC memory. You can create custom hardware that uses these standard parts to connect up these Raspberry Pi modules and save on space if needs be.

Laptop connectors? Does that mean I can plug it into my laptop?

No no, it’s not memory and it won’t fit. You would probably break the module or the laptop or both if you tried to force it in. There wouldn’t really be much use of it in a laptop though.

So really there’s no use for the Compute Module by a normal person at all?

Not exactly. Along with the Compute Module there’s also the Compute Module IO board, which you can plug the module into and get some of the inputs and outputs of the full Pi.

Some of the ports?

The module IO board is a bit like the Model A board: one USB, no ethernet. However, it also comes with two extended GPIO ports and a micro USB slave port. It does lack the analog Video out and headphone jack though, along with the SD card slot that is a little redundant.

So could I just get these instead of a Raspberry Pi?

You could but it would be more expensive than a normal Pi. You’d also miss out on the extra USB slot and ethernet port of the Model B, and it’s also a little bit bigger than the normal Raspberry Pi.

What exactly would you use the I/O board for then?

Well as we mentioned before, the Compute Module is mainly for people that would like to use the specific Pi processing parts in a smaller form- factor to build custom hardware. Before they can do that though, it helps to get prototyping so that developers can figure out exactly what they’re connecting and how to do it. The I/O boards help with this by offering just about every useful input and output and the bare minimum to display the Raspberry Pi on a screen if needs be.

Ah, so it’s a lot more for developers than for normal users. Is there anything stopping normal users from getting it?

Not really, no. It may have potential for being able to do more project work thanks to extra GPIO pins and an extra camera input, so it definitely wouldn’t be an awful purchase – just not as flexible or cheap as a Model B.

Fair enough. Say I’m a developer or a hobbyist with a need for the extra functions, where should I get one of these Compute Modules and boards?

When they’re in stock, you can grab them from the official Raspberry Pi vendors such as RS Components as part of a full kit.

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