Hardware Reference
In-Depth Information
he reason the Pi isn't provided with higher operating speeds in the irst place is related to
the chips' lifespan. he BCM2835 is rated by its manufacturer, Broadcom, to operate at a
speed of 700 MHz. Increasing the speed above this oicially-rated level may work, but it will
also have a deleterious efect on the lifespan of the chip. Unlike a desktop processor, SoC
designs rarely have much headroom for overclocking.
Overclocking Settings
If you're willing to take the risk of breaking the Pi—a process known as
bricking
in embedded
device circles—for the sake of a small performance gain, there are settings in
config.txt
which can help. he following settings control performance of the Pi's SoC:
❍
arm_freq
—Sets the core clock frequency of the CPU portion of the BCM2835, for a
boost in general-purpose performance. he default speed is 700 MHz.
❍
gpu_freq
—Sets the clock frequency of the GPU portion of the BCM2835, for a boost
in graphics performance across all operations. he default speed is 250 MHz.
Additionally, you can adjust individual portions of the GPU's hardware using the fol-
lowing options:
•
core_freq
—Sets the core clock frequency of the GPU, leaving the other frequen-
cies alone, to improve overall GPU performance. he default speed is 250 MHz.
•
h264_freq
—Sets the clock frequency of the GPU's hardware video decoder to
improve playback of H.264 video data. he default speed is 250 MHz.
•
isp_freq
—Sets the clock frequency of the image sensor pipeline, for improving
the capture rate of connected video hardware (such as a camera). he default
speed is 250 MHz.
•
v3d_freq
—Sets the clock frequency of the GPU's 3D rendering hardware, for a
boost in visualisation and gaming performance. he default speed is 250 MHz.
❍
sdram_freq
—Sets the clock speed of the random access memory (RAM) chip on
the Pi, to give the entire system a small increase in performance. he default speed is
400 MHz.
❍
init_uart_clock
—Sets the default clock speed of the
Universal Asynchronous Receiver/
Transmitter (UART)
, used to control the serial console. he default is 3000000, which
sets a speed of 3 MHz. Altering this is likely to have little efect beyond corrupting the
output of the serial console.
❍
init_emmc_clock
—Sets the default clock speed of the SD card controller. he default
is 80000000, which sets a speed of 80 MHz. Increasing this value can result in faster
reading and writing from the SD card, but can also lead to data corruption.
