Raspberry Pi A, Руководство пользователя, Страница: 117 / 314

C H A P T E R 6
T H E R A S P B E R R Y P I S O F T W A R E C O N F I G U R A T I O N T O O L
101
If you want to try overclocking your Pi, use the cursor keys to select an option from one of
the pre-set overclocks that appear on the next screen: None, Modest, Medium, High and
Turbo. Almost all Raspberry Pi models should be able to use the Modest setting, which sim-
ply increases the processor’s clock speed to 800MHz. Many will be able to use Medium,
which increases the voltage applied to the processor to reach 900MHz and additionally
increases the memory speed from 400MHz to 450MHz.
The remaining two settings may not work on all Raspberry Pi models. The BCM2835 proces-
sor is a complex circuit that will differ in its ability to be overclocked from unit to unit —even
two Pis from the same batch. The High setting increases the speed to 950MHz but requires
significantly more voltage than Medium or Modest to do so, which means more heat output
and a lower lifespan for the processor. The Turbo setting increases the processor to 1000MHz
while also doubling the graphics clock to 500MHz and increasing the memory clock to
600MHz. This offers the best performance, but has been linked to SD card corruption—
where files become unreadable—on certain Raspberry Pi models.
If you wish to make use of the Turbo mode, make sure you have backed up any important
files stored on the Pi beforehand. If you do start to have problems, drop down to the High
setting or lower and your Pi should return to normal.
When you have made your selection, press the Enter key and then press the Enter key again
to reboot the Pi at its new speed.
If you select a speed higher than the Pi can accept, it may not boot correctly. If you find your
Pi loads to a black screen or constantly restarts itself without prompting you to log in, you
have chosen too high a speed. Hold down the Shift key on the keyboard; this will temporarily
bypass the overclocking setting, loading the Pi at its stock speed. Once the Pi has booted,
release the Shift key and log in, then load
raspi-config
and enter the Overclock menu to
choose a more conservative setting.
8 Advanced Options
Choosing the Advanced Options entry with the cursor keys and pressing Enter will load the
Advanced Options menu (see Figure 6-4), which provides access to additional settings not
found on the Setup Options menu. If you enter this menu by mistake, you can go back by
pressing the Right arrow key twice followed by Enter to return to the main Setup Options
menu.