and a slower front side bus

Correct. Celerons have generally been one step below the high end processors for FSB speed. Current Celerons that fit into Pentium 4 boards run at 400mhz FSB, while the modern P4 chips run at 533.

In the past, raising the speed of the FSB was an easy way to overclock the Celeron and get good peformance boosts. But due to other crippling that Intel has done, a Celeron will not match a P4 of the same speed. (Unlike the Celeron 300A glory days).