This is 75 Odroid XU4 8 core systems to give 600 core total? Why do you downclock to 1.9GHz?
Yes, we're talking abount HC-1 modules. Well, downclocking them helps against thermal throttling at first.
Second is just about power usage.
The Samsung Exynos5422 processor comes with 4 big cores and 4 little cores.
First ones are the Cortex™-A15, which usually runs at 2.00 GHz, second ones are the Cortex™-A7, running at 1.4 GHz each.
Basically is like this:
[8 total cores]
core[0] 2.00 Ghz
core[1] 2.00 Ghz
core[2] 2.00 Ghz
core[3] 2.00 Ghz
core[4] 1.40 Ghz
core[5] 1.40 Ghz
core[6] 1.40 Ghz
core[7] 1.40 Ghz
Downclocking the first four ones, will save around 1Watt in terms of power usage (per board). And with only 5-6 h/m lost per board.
If thermal throttling kicks in, well you'll have everything forced to be setted more lower, like 1.4Ghz + 1.2Ghz. Maybe it could be more setting a performace mode using cpufrequtils but..I think it's not worth!
Anyway, if someone needs to know how to overclock or downclock those xu4 based boards, here's the code:
apt-get install cpufrequtils
cd /etc/default/
touch cpufrequtils
nano cpufrequtils
Add those lines for 1.9 GHz
ENABLE="true"
GOVERNOR="performance"
MAX_SPEED=1900000
MIN_SPEED=1900000
And the trick is done