This can occur because of any of the following reasons (and possibly others):
- another process is consuming significant amounts of system resources
- GPU processes may compete with CPU processes and produce lower results for both
- the MHz of your processor is actually different from what you think it is. It may also be running in a lower power/speed state.
- the client is selecting (or has been configured to use) a core that is not the optimal core for your processor.
- the client may be faster than previous versions due to core code improvements or new cores.
- your PC's memory cache is disabled (try looking in the BIOS).
- there is another hardware fault, such as bad RAM, a faulty timing clock, or something else that is causing the system to generally perform poorly. Usually you will notice related symptoms in other use of the machine too.