The Raspberry Pi has proved a popular – if difficult to get a hold of – low-cost computer. The Pi is powered by a Broadcom BCM2835 ARM system on a chip that features a VideoCore IV GPU and ARM1176JZFS CPU core. By default, the processor runs at 700MHz, but enthusiasts put it through its paces and found there to be more than a bit of headroom. Unfortunately, if your particular chip required a bit of extra voltage to run at higher frequencies, it would mean voiding your warranty in order to get the extra performance – until now, that is.
In a bit of good news for overclockers, the Raspberry Pi Foundation has announced that official overclocking will now be supported even when the processor has been over-volted. In the raspi-config file, you will be able to choose from one of five overclocking presets where the highest overclock will run the processor at 1GHz.
Interestingly, the overclocked frequency is managed by the cpufreq driver and can be dynamically adjusted. The processor will run at up to the frequency defined in your chosen preset as long as the temperature of the chip does not reach 85 °C. Also, the overclocked frequencies will only be applied when the SoC is under load. When idling, it will happily use less power by turning the clockspeed down. Further, when applying the higher clocks, you are also adjusting the GPU Core, SDRAM, and system bus speed.
When combined with other software fixes (below), the Raspberry Pi Foundation is claiming various performance improvements. According to the site, Linux benchmark nbench reports 52% better integer performance, 64% increased floating point performance, and a 55% improvement in memory.
Left: default clockspeeds, right: 1GHz overclock
Should your particular Raspberry Pi not boot after applying a higher overclocking preset, you can hold down the Shift key during boot to force the Raspberry Pi to revert to default clockspeeds. Then, you can back down to the next-highest preset to see if the Raspberry Pi is capable of running at that (though it would be a better idea to start at the lowest preset and work your way up). The Raspberry Pi Foundation recommends playing through a bit of Quake 3 as it is a good indicator of a stable overclock.
In addition to the new turbo mode, a fix has been applied to the USB driver to reduce the USB interrupt rate, which improves performance approximately 10%. Because even the LAN port is on the USB bus, reducing CPU load should help a lot in freeing up the limited resources of the ARM processor for other tasks. If you have Wi-Fi devices based on the RTL8188CUS chipset or is otherwise supported by Linux, it should now work with the Raspberry Pi out of the box.
In order to get all of the above improvements (among a couple of other minor tweaks), you can run the following command to update to the latest image:
“sudo apt-get update && sudo apt-get upgrade”
It’s nice to see continued support for the Raspberry Pi, and the ‘free’ overclocking performance is always a plus!
Image of Raspberry Pi hardware courtesy Gijsbert Peijs via Flickr Creative Commons. Thank you.
Read more about the $35 Linux-powered Raspberry Pi computer at PC Perspective!