Datasheet

VIPER Embedded Linux Development Kit Quickstart RedBoot

CPU Core Clock Frequency and the clock command

Versions of RedBoot on the VIPER up to and including V3I3 initialized the CPU clock to

200MHz at boot time. For version V3I4 this was changed to boot at 400MHz. The

current version (V3I5) no longer changes the clock rate, so it remains at the default

100MHz setting. However, this version introduces an additional command (clock),

which can be used to set the clock to any of the frequencies described in the CPU clock

frequency scaling section on page 22. The clock command takes parameters for the L,

M and N settings which control the clock speed as described in that section. The value

of N should be 10 times the actual value. Therefore, to set N to 1.5, pass the option

–n 15. For example:

To set the clock frequency to 300MHz power saving mode: •

•

RedBoot> clock –l 27 –m 1 –n 30

To set the clock frequency to 200MHz performance mode:

RedBoot> clock –l 27 –m 2 –n 10

If you have an AEL Development Kit, the default AEL boot script initializes the clock to

400MHz.