Introducing turbo mode: up to 50% more performance for free
Posted on September 19, 2012 by eben
Since launch, we’ve supported overclocking and overvolting your Raspberry Pi by editing config.txt. Overvolting provided more overclocking headroom, but voided your warranty because we were concerned it would decrease the lifetime of the SoC; we set a sticky bit inside BCM2835 to allow us to spot boards which have been overvolted.
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. 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.
You 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. 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.
What does this mean? Comparing the new image with 1GHz turbo enabled, against the previous image at 700MHz, nbench reports 52% faster on integer, 64% faster on floating point and 55% faster on memory.