Hardware Reference
In-Depth Information
Pretested Overclock Presets
Newer versions of the Raspberry Pi firmware contain the option to choose between
five overclock (
turbo
) presets that try to get the most performance out of the SoC
without impairing the lifetime of the Pi. This is done by monitoring the core temper-
ature of the chip and the CPU load and dynamically adjusting clock speeds and the
core voltage.
So, when there is a low demand on the CPU, or it is getting too hot, the performance
is throttled down, but if the CPU has much to do, and the chip's temperature allows
it, performance is temporarily increased, with clock speeds up to 1 GHz, depending
on the individual board and which of the turbo settings is used.
Table 1-4
details the
current settings of the five overclock presets.
Table 1-4.
Overclock presets
PRESET
ARM
CORE
SDRAM
OVERVOLT
None
700
250
400
0
Modest
800
250
400
0
Medium
900
250
450
2
High
950
250
450
6
Turbo
1000
500
600
6
If you are running a current version of Raspbian, you will notice that the
raspi-
config
tool has support for configuring your Pi into any of these five presets. For other
distributions, you will need to define the preset you want to use in
/boot/config.txt
by passing the values for each option individually. For example, to set the Medium
preset, add these lines to your
/boot/config.txt
:
arm_freq=900
core_freq=250
sdram_freq=450
over_voltage=2
Also, just because the Turbo setting has been known to work with some Raspberry Pi
units, that doesn't mean it will work with yours. Quite a few users have reported SD
card corruption when trying to run their Raspberry Pi at that overclock preset.
Overvolt for Higher Performance
HACK 07
Overvolting, also known as “dynamic voltage scaling to increase voltage,”
is a trick to get more performance out of an electrical component.
The circuits in your Raspberry Pi are made up of transistors that act as logic gates or
switches. The voltage at these nodes switches between a high voltage and a low volt-
