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Overclocking: do you do it & how do you check for stability?

Wed Dec 30, 2015 11:08 pm

Hi everyone.

Do you overclock your raspberry pi? If you do, what settings do you use, and how do you check to make sure your overclock is stable?

For me, I have a raspberry pi 2, and these are the settings I use in config.txt:

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temp_limit=76     #I set this 9 degrees lower than the default value, just to be careful
arm_freq=1000     #100MHz faster than default
core_freq=350      #also 100MHz faster than default
over_voltage=1     #my stability tests failed without this. I personally won't ever set this to be higher than 2
I tested its stability using a simple script I wrote, which uses 'lame' to encode and then decode a short song in .wav form, and then checks the md5sum of the final output to see if it gets the same end result every time (and all the files are written to a ramdisk/tmpfs to avoid wearing out the microSD card).
I also wrote another similar script that uses 'imagemagick' instead of lame. I ran four instances of these scripts to load each of the raspberry pi's cores, and left them running for about two hours (but with a desk fan blowing on the rasberry pi to prevent overheating)

I know it's probably not an optimal way to test for reliability, but it seems to have worked well enough.
I can post the scripts I made if anyone wants them.

Anyway, if you overclock, how do you personally test for stability?

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Re: Overclocking: do you do it & how do you check for stabil

Thu Dec 31, 2015 3:30 am


I'm using this

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I got these from https://wiki.debian.org/RaspberryPi
I didn't do any test on purpose. The Debian wiki says it works, so I'm trying with it. My plan is if it fails, I would switch back.

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Re: Overclocking: do you do it & how do you check for stabil

Thu Dec 31, 2015 11:56 am

I found memtester useful: "sudo apt-get install memtester".

Then something like (for the Pi2): "sudo memtester 800m 10"
Then add some small CPU bound processes to ensure all four cores are at 100% all the time (check "id" in top - it must be zero).
You could also run multiple instances of memtester say checking 200m each.
If it all runs for a day like this, you know its stable. Usually it will fail within an hour or so depending on your overclock and the cooling.
For my headless Pi2:-

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"over_voltage_sdram" sets all three sdram voltages in one go.
You may continually monitor the temperature with bcmstat.sh.

The sdram seems to have the least margin. You might get some extra stability with "disable_pvt=1" which sets the dram refresh rate to a conservative value at a small cost to performance. Without this, the temperature of the sdram is measured twice per second and an optimal refresh rate set.

Additional cooling may allow lower voltages for the same level of stability.
Pi4 8GB (Raspberry Pi OS 64-bit), Pi4 4GB, Pi4 2GB, Pi1 Rev 1 256MB, Pi Zero

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