You must have Enhanced Intel SpeedStep® Technology enabled (the equivalent of the i7 Turbo Boost). This allows you to obtain more performance under load. DX-Diag must mesure the highest possible frequency obtainable by your CPU.
Yes the is no problem, as long as your computer doesn't freeze or reboots when the CPU is fully loaded. If that starts to happen, you can try increasing the Vcore a little bit. It should solve your problem. If it does not, simply disable this function.