The graph shows utilization, which is not the same as clock speed, so the graph itself is fine, but if the clock speed never changes from base speed, it seems that Intel SpeedStep is disabled in BIOS.
It isn't unusual for BIOS settings to be changed/messed up after an update. The general recommendation for any BIOS update is always to do a "reset to factory defaults" or "reset to optimized defaults" in the BIOS after an update to make sure the BIOS settings have sane values.
After that you can further fine tune the BIOS settings with any additional special settings if needed (if you are not aware of any special BIOS settings you probably don't need them).
So try resetting your BIOS settings and see if that fixes the problem.