On Thu, 16 Sep 1999, Mark Huang wrote:
> Is there a way to update the SA-1100's PPCR register and change the core
> clock frequency on the fly after booting Linux? I've tried running the
> assembly code that I use to set the core clock before booting, but that
> just hangs the system usually.
This is not something you would want to do too often, as that register
controls the PLL that drives the clocks. When you change the register,
I believe the clock is gated off for a while to give the PLL time to
settle into the new rate. That means that all peripherals are dead for a
while too. But I can see how you might get a power saving if you can find
the appropriate moment to do it.
BTW, I think parts like the EP7211 will have a register that varies the
clock rate over a much smaller set of values, by switching divider values.
That avoids the clock while the PLL settles, so it's more useful for power
saving without interrupting peripherals.
Cheers,
- Ben.
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Ben Williamson [EMAIL PROTECTED] http://www.pobox.com/~benw/
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