On 3/11/2014 10:45 PM, Jon Elson wrote: > On 03/11/2014 07:57 PM, Charles Steinkuehler wrote: >> On 3/11/2014 7:23 PM, Jeff wrote: >>> Hi, >>> >>> Got it! Thanks. It is now at 990.68 MIPS with the newer kernel. >>> >>> > So, what is going on with the older machinekit installs? Do > they actually not > run the CPU at rated speed? I did notice that some things, > like generating > an initial SSH key took a VERY long time, and when I did > "more /proc/cpuinfo" > it showed a very low clock speed, like 200 MHz, but I wasn't > sure I could > trust that number.
CPU frequency scaling was disabled in the kernel configuration as recommended by the Xenomai folks. The problem is, that leaves the CPU frequency set by the boot loader with no way to change it. Different versions of the boot loader run the CPU at different frequencies. My boards would typically run at 500 or 750 MHz, but some run as slow as 350 MHz or so. I have since added back the frequency scaling support, but only compiled in the "performance" profile, so the CPU runs as fast as possible and stays there. The extra latency is caused by the CPU switching operating frequencies (which shuts *EVERYTHING* down for a few hundred uS or more while internal PLLs stabilize to their new frequencies), so this isn't an issue if you don't actually change operating frequencies on the fly. -- Charles Steinkuehler char...@steinkuehler.net
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