Good morning,
As promised, here are results from my RPi 3 A+ overclocking tests.
I made over 20 tests ranging from “1400 MHz with -2 over voltage option” to “1500 MHz with 1 over voltage option”. No other changes were made to other parameters.
Only two tests provided stable RPi 3 A+ operation:
a) 1450 MHz with 0 over voltage (3,57 % overclock);
b) 1475 MHz with 0 over voltage (5,36 % overclock).
Stability of case a) was achieved in all 4 RPi 3 A+. Case b) was only stable in 2 of my RPi 3 A+. Please check “RPi 3 A+ Overclocking Feedback a.png” for detailed information.
Images “RPi 3 A+ Overclocking Feedback b.png”- general info -, “RPi 3 A+ Overclocking Feedback c.png” - CPU Loads info - and “RPi 3 A+ Overclocking Feedback d.png” - Temperature info - provide detailed information gathered from RPi-Monitor running on my “RPi 3 A+ A @ 1475 MHz with 0 over voltage”. This machine is running without any problems from 2020/07/26. “CPU Loads” and “Temperature” drops on the 2020/08/10 are due to maintenance reboot. Similar behavior can be verified for my “RPi 3 A+ B @ 1475 MHz with 0 over voltage” and for my “RPi 3 A+ C and D both @ 1450 MHz with 0 over voltage”
Operation temperature is around 50º C. Temperature values change over time reflect decrease of room temperature. This operation temperature is achieved by using 5 cm fan operating over RPi 3 A+ cpu (using adapted RPi case). No tests were done without fan operation so, no temperature limit check was done for all tests made.
RPi 3 A+ run BOINC software for Universe@home project. All 4 cores run at full speed 24h / day. RPi 3 A+ display circuitry is switch off (running /usr/bin/tvservice -o) on all RPi’s.
During my tests some conflicting CPU speed information was provided by different tools:
- DietPi-Config (please check image “RPi 3 A+ CPU Speed.png”) reports CPU speed defined in “/boot/config.txt” (please check image “RPi 3 A+ CPU Speed.png”);
- Same speed is reported by RPi-Monitor (please check image “RPi 3 A+ Overclocking Feedback b.png”);
- lscpu and DietPi CPU utilities report 1500 MHz (please check image “RPi 3 A+ CPU Speed.png”). lscpu is probably reporting CPU spec and not current operation speed (it does the same for my ASUS TB) but RPi 3 A+ base spec is 1400 MHz. DietPi CPU reports current CPU operation speed in all my other RPi’s and ASUS TB.
I have no knowledge to verify the cause of this behavior, present in all RPi 3 A+ (running at 1450 MHz and 1475 MHz).
RPi 3 A+ is a wonderful little board but is very sensible to changes in CPU speed (not due to temperature, but to system stability, from my experience). 3,57 % or 5,36 % is almost no overclock.
I hope this information is useful.
Best regards,
Paulo Reis