Hardware Reference
In-Depth Information
As an example, to overclock the CPU to 800 MHz, the GPU to 280 MHz and the RAM to 420
MHz, enter the following options into config.txt , one per line:
arm_freq=800
gpu_freq=280
sdram_freq=420
As with adjusting the display coniguration, any changes made regarding overclocking won't
take efect until the Pi is restarted. To return the settings to normal, you can either delete the
entire config.txt ile or—if you're using it to control the display settings as well—simply
delete the lines that deal with overclocking, and then restart the Pi.
Overvoltage Settings
If you're overclocking your Pi, you will eventually hit a brick wall past which the device won't
go. he precise point at which the Pi won't reliably overclock depends on the individual
device, due to natural variations in the chip introduced during the manufacturing stage. For
some users, this limit may be as low as 800 MHz; others may ind that they can push their Pi
as high as 1 GHz (1,000 MHz) without issue.
If you want to eke a little more performance out of your Pi, there is a way to potentially boost
this upper limit: a process known as overvoltage or overvolting . he Pi's BCM2835 system-on-
chip processor and the associated memory module usually run at 1.2 volts. It's possible,
although potentially inadvisable, to override this default and force the components to run at
higher or lower voltages. Boosting the voltage means boosting the signal within the chip,
making it more likely to hit higher speeds—it also means that the chip runs hotter, reducing
its lifespan dramatically compared to overclocking alone.
Setting any of the voltage options in config.txt causes a fuse within the BCM2835 to trip
in a way that cannot be reset. It's a foolproof way to tell if someone has been attempting to
overclock the chip outside its rated speciications, and renders your warranty null and void
even if the cause of failure is unrelated to overclocking. If you return a Pi for replacement under
warranty and the fuse is tripped, it will not be replaced . Do not attempt to overvolt a Pi that you
cannot afford to replace yourself.
WARNING
Unlike the previously described settings, which are provided in config.txt as absolute
values, the voltage adjustment is carried out using values relative to the Pi's stock 1.2 V set-
ting. For each whole number above zero, the voltage is increased by 0.025 V from stock. For
each whole number below zero, the voltage is decreased by 0.025 V from stock.
 
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