2017-02-21, 23:45
(2017-02-21, 16:03)popcornmix Wrote: gpu_freq isn't a specific clock but is a shorthand for setting core_freq, v3d_freq, h264_freq and isp_freq (if otherwise not set).
These days there are separate PLLs for core_freq and the other 3. So core_freq can be set arbitrarily compared to v3d_freq/h264_freq/isp_freq.
v3d_freq/h264_freq/isp_freq need to all be integer divisors of the PLL. The simplest option is to set them all the same.
For HEVC, the sdram, arm, core and v3d are the important clocks (roughly in that order, but they are all significant).
In Milhouse's config.txt the core_freq line is redundant (it defaults to gpu_freq if otherwise unspecified).
But it would work perfectly fine with, say core_freq=513, as core_freq has its own PLL.
However:
gpu_freq=500
v3d_freq=513
wouldn't be satisfied exactly as v3d shares a PLL with h264/isp. I think you would get 513 for all 3 clocks.
Thanks Popcornmix, some very useful info there. I didn't know that it was now possible to set core & gpu independently :-( is that true for all pies, so a software change, or only pi2 or pi3? I've tried Google but couldn't find any definite answer.
Thanks again Kevin.