rpm meter count error-8051 microcontroller

dear friends
me designing a rpm meter using 8051. ( a disc with 6 holes) i am using two interrupts one external interrupt INT1 for external pulse and timer interrupt TR0 for counting the pulses.the refershing rate of data is 10 sec. but i m getting error in counting.the count is not correct. both the interrupts are not working correctly.
can u help me out for it.

thanks
amit

It seems to me that you only need one external interrupt ( for counting the pulses ).. and an internal counter as a time base..
how are you counting them anyway ? with a A/D converter or a comparator?
and why six holes in the disk?