Raspberry Pi hits the 1GHz turbo mode afterburners



Posted by Trent Nouveau

The folks over at the Raspberry Pi Foundation have thus far supported modders who overclocked and overvolted the uber-mini devices, at least in principle. 



As RP Foundation trustee Eben Upton points out, overvolting does provide more overclocking headroom - but ultimately voided the warranty over concerns that it would decrease the lifetime of the SoC.



"So we set a sticky bit inside BCM2835 to allow us to spot boards which have been overvolted. [Since then], we've been doing a lot of work to understand the impact of voltage and temperature on lifetime, and are now able to offer a 'turbo mode,' which dynamically enables overclock and overvolt under the control of a cpufreq driver, without affecting your warranty," Upton wrote in an official blog post.



"We are happy that the combination of only applying turbo when busy, and limiting turbo when the BCM2835′s internal temperature reaches 85°C, means there will be no measurable reduction in the lifetime of your Raspberry Pi."



According to Upton, Raspeberry Pi owners who download the latest version of Raspbian Linux operating system can now choose from one of five overclock presets in raspi-config, the highest of which runs the ARM at 1GHz. 



"The level of stable overclock you can achieve will depend on your specific Pi and on the quality of your power supply; we suggest that Quake 3 is a good stress test for checking if a particular level is completely stable," he explained.



"If you choose too high an overclock, your Pi may fail to boot, in which case holding down the shift key during boot up will disable the overclock for that boot, allowing you to select a lower level."



So what does turbo mode mean for the overclocker in terms of raw specs? Well, nbench is reporting 52% faster on integer, 64% faster on floating point and 55% faster on memory.

Upton also noted that the latest iteration of Raspbian Linux allows usersto enable a core temperature widget for the lxde taskbar to see how close to 85°C the board is, while a cpufreq widget displays the current ARM frequency when a user hovers over it.

"In addition, we have enabled [a fix for] the USB driver, which reduces the USB interrupt rate, improving general performance by about 10%. [Plus] WiFi is now supported out of the box - if your WiFi driver is supported by the default linux tree, or is based on the popular RTL8188CUS chipset.



"Simply boot the image with the WiFi dongle plugged in (a powered hub is recommended). Run startx and select 'WiFi Config'. You can scan for wireless networks and enter your wireless password and connect from the GUI. There is no need to install additional packages or scripts," he added.