hehe shoot, such an obvious reason huh?
but hmm wondering why the LED is not blinking exactly HALF the speed (it's blinking around quarter or less the speed) if I'm using a 4 mhz. maybe it has do with the fact that the frequency dictates the number of instructions executed per second, to which the LED blinking might not be linearly proportional because of the presence of other operations in the code. just ordered some 8 mhz crystals; will do some timing tests soon.