At the moment the PS7 is using three PLLs to generate its clocking tree.
One for the DDR, one for the ARM and one for the IO. This allows to run all
components at their respective maximum clock and extract maximum
performance from all components.
With some slight modifications it is possible to trade maximum performance
for a reduction in power consumption by using the same PLL for all three
sets of components and disabling the other two PLLs.
The CPU is now running at 500MHz rather than 666MHz and the DDR memory at
500MHz rather than 533MHz. This reduces power consumption by ~125mW.
This is OK since neither of them is a bottleneck for overall system
performance.
In addition software will downclock the CPU to 250MHz when full performance
is not required.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>