I have now checked at TI E2E, and TI said/confirmed (as I
expected), that it’s the voltage more than the frequency which age the
chips => 600MHz and 720MHz are both considered overdrive modes for both 600-
and 720-grade silicon. Please see answer here: https://e2e.ti.com/support/dsp/omap_applications_processors/f/447/p/62063/223487.aspx#223487
The highest totally safe operating freq (100K POH) is therefore 500MHz regardless of chip-grade. Increasing to 600MHz or 720MHz will statistically shorten the chip lifetime (and increase the power consumption), so I recommend keeping default at 500MHz, but it might be an idea to introduce a dummy mpurate variable set to 500 in U-boot for users to easily figure out what to change in order to increase the speed to i.e. 600MHz or 720 MHz should the need/want.
The above being said. The complete idea with OMAP is to run at as low a frequency as possible when not needing the processing power and just scale to something higher on the fly when needed. In the longer run I therefore think it’s best to just let Linux idle-thread/frequency-governor handle the CPU scaling (with a user defined max-setting). There is already some support for this, but to be honest I haven’t checked it for a long time…
Best regards and thanks – I hope this clarified the topic?
SSC Solutions ApS - Denmark - www.ssc-solutions.dk