My processor is 2.4ghz or 3.4ghz??

I run win Vista ultimate in 946gz board and pentium d processor 3.4ghz. When i saw my cpu detail in tweak vi, it showed that my current clock speed is 2.4 ghz and maximum is 3.4ghz. Does it mean that my cpu is not running as it should or it is common. if it is not running fast then How can i increase its speed.