That's how you overclock.
Unless you buy an extreme edition or black edition CPU, multiplier are locked upwards, meaning the only way to increase a CPU's speed is by increasing the FSB.
So when you buy that E4500, it will be running @ 11x200 by default.
It's simple math.
11 = multiplier
200 = FSB
11x200 = 2200 MHz.
Make sense?
To overclock, you increase the FSB.
So let's say you went into the bios & increased the speed of the FSB from 200 to 250.
That's 11x250 = 2750 MHz.
And so on.
RAM speed also coincides with this, via ratios, or fractions.
Common one would be 1:1, which means the RAM operates at the same frequency as the FSB.
But there are other options, such as 4:5, 2:3, 1:2, etc.
At stock speeds, your CPU is 200 MHz FSB.
If you set the RAM ratio to 1:2 (iow, RAM is twice as fast as the FSB), you'd have RAM running @ 400 MHz, which is DDR2-800 (400 MHz x 2 - double data rate).