dietpi-config > Tools > Benchmark 
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With v6.17 those results can be uploaded too, to have a average/min/max comparison 
: https://dietpi.com/survey/#benchmark
As mentioned, we did not yet implement the SDcard overclock setting, as we need to be very sure, that the end user SDcard supports it. If the SDcard does not work with 100MHz, then you will at first not see any errors or issues. The data will corrupt silently and when you recognize, it’s too late. So we need to be very sure, when we want to implement this!