Raspberry Pi 512MB £25

6th Nov 2012 | 13:00

Raspberry Pi 512MB

A sensational educational tool that doubles as hacker paradise - now with double the memory

TechRadar rating:

4 stars


Supremely affordable; Lots of interfacing options; Almost 100% open source; Massive community; Many example projects


No VGA connectivity; Lack of decent starter guide; Tricky to install; Modest CPU performance; No ARMv6 Flash support


The humble Raspberry Pi came to life as little more than a prototype in late 2011, knocking around some trade-fairs. But even at this point, it had been in development for over four years.

The brainchild of Eben Upton, who started piecing together the Pi on the longest piece of breadboard he could buy from Maplin, its principal motivation was to make computing accessible, with a plan to give the boards to school kids in the hope they'd get enthusiastic about hacking on the devices, just as the Raspberry Pi's founders had done with their home computers in the 80s.

It was this 80s computing meme, along with co-conspirator David Braben's address book famously plundered for contacts and the idea that programming should be taught to everyone, that has helped the Raspberry Pi get phenomenal traction.

Just a few months after those prototypes were shown at trade shows, over 200,000 people registered their interest for the first 'Model B' boards, 20 times the capacity of the first production run, and the rest is history.

The Raspberry Pi sold half a million units in 6 months, not into the educational market it was designed to revolutionise, but into a wide demographic of hackers, makers and tinkerers.

Complete PC

Pi config

This is a device that can legitimately be described as a fully-fledged PC, albeit one that's embedded into a diminutive printed circuit board, measuring just 85.60 mm by 53.98 mm. The CPU isn't powerful, an ARMv6 running by default at 700Mhz, but it can be powered by a USB cable, and even batteries, and is capable of running a graphical environment with accelerated video - through either an HDMI port or a composite RCA jack suitable for televisions.

The lack of old-style VGA is a problem when you consider there are now so many old redundant monitors, but this oversight is more likely to be a limitation of the SoC hardware than a shortfall in design.

Either way, the Pi's killer feature isn't the hardware specification, it's the price. The Raspberry Pi can be yours, delivered, for around £25 - and that includes 20% UK VAT.

Supply and demand

Pi memory

The demand has been such that the cheaper 'no networking' Model A has yet to be released.
But in the short time that the Model B has been available, there have been 3 revisions. The first two, marked revisions 2 and 3 when you check the processor identifier, differ only by the removal of a D14 component, originally situated beneath the HDMI port, and some fuse modifications.

But the third update, officially called 'Revision 2.0' and available from the end of September, packs more significant updates, despite looking almost identical to previous versions. The 'almost' refers mostly to the additional two mounting holes, which should make it easier to attach your Pi to a case or anything else, and a supplementary 'P5' header, consisting power, ground and 4 additional connections to add to the array of GPIO ports.

The biggest improvement is the amount of RAM. This doubles, from 256MB to 512MB whilst keeping the price the same, making the Raspberry Pi much more feasible for running desktop applications. On our system, a default boot to the command line left us with 384.4 MB free, rather than a measly 126 MB on the first model.

The general purpose pins have also been tweaked, reversing those used for I2C, a widely used data bus system. GPIO is where the Raspberry Pi overlaps with other projects like the Arduino, because it allows the user to build their own hardware and hook it up to both digital and analog signals managed from software running on the Raspberry Pi. The advantage with the Pi, of course, it that you can run a full operating system on the hardware, rather than bytecode.

The official operating system is a Debian-derived Linux distribution called 'Raspbian'. This too has changed little over the months, and while we've been able to successfully install the system onto a 2GB SD Card, you'll have a better experience with more storage, as you'll have more freedom to add your own files.

If you've used the command-line on a Debian-based distribution before, such as Ubuntu, you shouldn't have any problems as many of the same commands and configuration options will be familiar. But even if you've only ever used Windows, the command line isn't that difficult. Arm yourself with a couple of tutorials and start investigating. If you break the installation, the worst that can happen is you'll need to reflash your storage with a new version of the distribution.

Specification and Performance

Raspberry Pi

Booting the distribution for the first time, you'll be asked to run a custom configuration tool called 'raspi-config', recently updated for Revision 2.0. This tool is one of the big advantages of using the official distribution over one of the various alternatives.

From the configuration tool, you can expand the size of the filesystem on your memory stick, enabling your installation to make use of all the space, alter the keyboard layout and change passwords, as well as setup the graphical desktop to start at boot.

Advanced options allow you to configure the split between the amount of RAM allocated to the CPU and the GPU, which is great if you know you want to play with gaming or provide maximum resources for your applications.

Overclocking is now official, and the configuration tool can boost the default 700 Mhz CPU speed, the 250 Mhz of the core and 400Mhz RAM up to a much-improved 1000 Mhz, 500 Mhz and 500 Mhz, respectively. You might need more than simple bus power to feed the Pi under these circumstances, and heat dissipation might cause problems, but it worked for us from a normal USB hub.

Overclocking is also dynamic, so the new frequency will only kick in when needed and will automatically revert to the default speed when the core temperature reaches about 52 degrees celcius. You can see this in action by watching both the 'thermal_zone0/temp' and the 'scaling_cur_freq' values in the sys virtual filesystem.

In our tests, without overclocking, we created a 100 MB file from /dev/urandom in 151 seconds, and at 1 Ghz, in 118 seconds. Compressing these files with bzip2 took 439 seconds at 700 Mhz, and 333 seconds at the maximum overclocking value. This suggests around a 30% performance boost, a value which could probably be easily improved with better cooling. But as ever, benchmarking is far from an exact science, and your mileage will vary.


How you go on to use the Raspberry Pi is up to you. Thanks to the use of Debian, you can install exactly the same software you can with any other Linux distribution. If you want to access the GPIO pins, there's a command line utility and several APIs for accessing the functionality from other languages.

But as the Raspberry Pi is now firmly in the domain of the hackers, new solutions are appearing daily, including GPIO control through a web interface and countless other projects using the Pi at their heart. Programming is easily catered for by installing anything from Python to the recently announced TinyBASIC, if you're after that authentic 80s experience.

We liked

The Raspberry Pi now has a thriving online community and the constantly expanding wiki provides all the information a beginner needs to know, although it could benefit from being condensed into a simple guide for beginners.

The new devices are even built at Sony's manufacturing facility in Pencoed, Wales, and the team has set an important precedent by working with Broadcom to release parts of the VideoCore interface under the terms of an open source licence.

We disliked

The Raspberry Pi does have its problems. The CPU is old technology, and it's not as quick as some of its competitors. The lack of a case could limit its application, although there are third-party cases available.

And if you're new to Linux, there's also a steep learning curve to tackle, as you'll have to successfully write an image to a memory card, update packages and use the command line before you even get to a graphical environment. But this is all part of the challenge, and making things easier might limit the device's flexibility

Final verdict

This flexibility is wonderful, but it doesn't mean anything without the accompanying low cost. By pricing the Raspberry Pi so cheaply, its creators have gifted a new generation the ability to experiment without the fear of destroying either valuable equipment or ambition.

And this is the key to the Pi's success. It wipes away the decades of stuffy formality that has traditionally surrounded computer science, replacing it with a world of seemingly infinite possibilities. Admit it, even you've got an idea for something to try on the Raspberry Pi, and that's why it has been, and will continue to be, such a success.

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