What speed does the CPU actually run at?

There’s a thread about running the CPU on the unmatched at 1.2GHz on Ubuntu. The spec sheets say that the CPU’s speed is 1.2GHz, so what is the default on Ubuntu, and is that the same as booting the Freedom U SDK image?

The speed is set by the bootloader, in the fsbl. The original SiFive OpenEmbedded 2021.03 release set the speed to 1.0GHz. The followup 2021.03.1 release set the speed to 1.2GHz. The Ubuntu guys accidentally took the wrong fsbl and ended up with an OS that runs at 1.0GHz. They just need to fix their image to use the right fsbl and it will run at 1.2GHz.


Thank you very much for the info. I’ve been preparing a new video for YouTube using Ubuntu, running some games and benchmarks - wanted to make sure that my information is correct before uploading anything.

I got my video up now, including the CPU info. I’m not 100% happy with how it came out, but if I spent any more time editing it then I’d go mad…

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