But the output you posted correctly shows 400Mhz...?
BTW, the CPU speed detection is based on known timings from known CPUs. If the code can't correctly detect the CPU, or has no timings for that CPU, the MHz speed is a best guess which will likely be wrong.
Yup, that 400MHz came from the non-debug test. I was surprised to see that DSTUB came up with a different value.