Neil Turner's Blog

Blogging about technology and randomness since 2002

Raspberry Pi – what makes it interesting

Photo of a Raspberry Pi
Photo by ‘Jwrodgers‘, under CC BY-SA License.

On Wednesday I talked about the possibility of building a media centre PC using a Raspberry Pi. I’ve spent quite a bit of time looking into the Raspberry Pi, as to whether it would be suitable for this purpose, and the more I’ve read about it, the more fascinated I’ve become. It’s a very interesting little device that makes some big changes to the way we see computers.

It’s a fully-functioning PC, but it’s only the size of a credit card

I own a Mac Mini, which is pretty small as desktop computers go, but this thing is actually tiny. Its small size is partly down to it not having a number of components that are normally standard in other PCs, namely:

  1. No CMOS battery. Pretty much all computers, including desktops, have a small button battery on the motherboard. This ensures that the computer can remember some basic settings, and namely the current date and time, when it is switched off. The Raspberry Pi does away with this, freeing up space and reducing the number of components, and therefore the cost. The side effect of this is that, when you first boot the computer up, the time will be wrong. However, as long as you’re connected to the internet, the computer will contact a time server using NTP and set the correct time. Although this may be a problem on the Model A Raspberry Pi as this doesn’t come with an ethernet socket.
  2. No PCI sockets. Or AGP, PCI Express or anything like that. The ethernet socket is effectively connected using USB, which is also why it uses 10/100 Mbps and not Gigabit Ethernet – USB 2.0 is capable of a maximum of 480 Mbps.
  3. Display output is HDMI or RCA. In other words, no huge VGA or DVI sockets.
  4. No built-in storage. There isn’t a hard disk, or solid state drive, included. You can add an external USB hard drive if you want, although the device always boots from an SD card.
  5. No on-off button. To turn the device on, plug it in. To turn it off, un-plug it. Simples.
  6. No PSU. There isn’t a bulk power supply unit – the whole device takes DC power.

It’s easy to run multiple operating systems

To run multiple operating systems on a regular PC, you usually have to mess around with partitioning disk drives and setting up a boot menu, and all the while hoping that you don’t corrupt all of your data in the process. On the Raspberry Pi, you just need an SD card for each operating system. Then, when you want to change from one to another, turn the device off, take the SD card out, and put a different one in.

A big advantage of this is that you can create one master SD card, with a ‘clean’ installation on it, and then work from a copy on another SD card. If you mess up the copy, then just wipe the card and replace it with the contents copied from the master. And SD cards are pretty cheap these days – £10 will buy you a good 16 GB class 10 card.

It requires very little power

Because the Raspberry Pi comes with an ARM processor, as opposed to a more power-hungry x86 processor from the likes of Intel, you can run one using a phone charger. All it needs is 5 volts of DC power, and it uses micro-USB which has been standard on many phones for some years now. Even if it is plugged into the mains all of the time, it will use very little electricity. You could also run it off 4 AA batteries if you wanted to.

You can install a wide variety of operating systems

There’s a list on Wikipedia. The ‘default’ is called Raspbian (which I sing to tune of Boney M’s Rasputin), based on Debian Linux. Gentoo and Slackware Linux can also be installed, as these are generally compiled from source to target the particular computer anyway. Sadly, Ubuntu dropped support for this type of processor in 2009, some time before the Raspberry Pi was announced, so the most popular Linux distro is notable by its absence.

You could also install one of a number of smartphone operating systems. Android is the obvious one, but Firefox OS and WebOS (which was used on the short-lived Palm Pre and HP TouchPad) are also available.

More obscure operating systems include Haiku, which is clone of BeOS, and Risc OS which is descended from the Acorn Archimedes computers that I used at school in the early 1990s.

Theoretically the ARM processor in the Raspberry Pi could be capable of running Windows RT or iOS but without the collaboration of Microsoft or Apple this is unlikely.

You can access the GPIO pins

There are a bank of GPIO pins that are available for you to use for various projects. This is in-line with the Raspberry Pi’s aim of being an easily ‘hackable’ computer that can be used to teach programming. Not many other computers allow such low-level access. It should permit some projects that would otherwise require a device such as the Arduino, which is more expensive and arguably more limited.

It has a surprisingly powerful GPU

The CPU is, apparently, broadly equivalent to a Intel Pentium 2 at 300 MHz. This would put it amongst computers that are pushing 15 years old. However, its GPU – i.e. its ‘graphics card’, is actually quite powerful – again, broadly equivalent to that in the original Xbox. Yes, that is quite old too, but still pretty good for such a small device. And it includes some more modern features, such as accelerated decoding of h.264 HD video, which make it more useful for modern-day purposes.

And the basic Raspberry Pi only costs $25

Because it’s such a simple machine, it’s possible to buy the basic Model A for $25 – and the better Model B, with ethernet, double the RAM and an extra USB port, for $35. That’s amazingly good value. It’s also small enough to be fitted inside other things for various projects.

I’m really looking forward to buying one.

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