Monitoring software uses different Windows timers to calculate the MHz. When overclocking the BCLK in Windows, these timers can get out of sync so the high performance timer might not be accurate. You can try running
Let it run for about 100 seconds and it should show both of your timers running at the exact same pace. If there is a problem, post your results.
You can change what source Windows uses for its high performance timer function. Open up a command window and enter this line.bcdedit /set useplatformclock true
You will need to reboot to get Windows to switch to a different timer.
If you want to go back to the original timer that Windows uses then open up a new command window and enter this.bcdedit /deletevalue useplatformclock
You won't hurt anything trying a different timer. The alternate timer is based on a chip that runs at a fixed frequency of exactly 14.31818 MHz. I prefer using this timer since it runs at the exact same speed even if you adjust the BCLK in Windows. The latest version of CPU-Z seems very accurate at calculating the BCLK. RealTemp is overdue for an update and Windows 8 is a work in progress.
Edit: Here's a couple of examples of what WinTimerTest shows; first when your timers are broken and the second picture is after Windows was switched to the 14.31818 MHz timer.
http://img96.imageshack.us/img96/8417/timerfix.pngEdited by unclewebb - 12/1/13 at 2:12pm