Underclocking: cpufreq driver for sheeva/guruplug... possible?

[doragasu]

I was wondering if the CPU in the plugs has an internal PLL that can be changed on the fly. It would make possible to code a cpufreq driver to save power and avoid overheats when CPU load isn't high.

Is it possible to make this kind of driver for the plugs? Is anybody working on it? I have read in page 61 and 67 of the 88F6281 hardware specifications that the chip has a PLL, but I don't  know if it can be changed on the fly, and if there are other supported combinations rather than the ones listed in page 61.

Also, is there other way to underclock the CPU using only software? Maybe changing some settings in the kernel?

[doragasu]

Nobody knows about this? When is the PLL supposed to be configured? Kernel? U-Boot? I have browsed U-Boot sources and haven't found anything related to the PLL, so I suppose it's automatically configured by hardware.

Maybe it would be possible to change this config in U-Boot...

[hojnikb]

Yeah i would like to know that too 
This things can get hot very quickly

[restamp]

Not exactly what you're asking for, but have you looked at the following:

http://plugcomputer.org/plugforum/index.php?topic=260.msg1541#msg1541

http://openplug.org/plugforum/index.php?topic=272.0