Timer Simulation

Hi,

I am performing simulation on ARM7, LPC2368 micrcontroller using Keil IDE UV4. I had written a delay function using timer. This works perfectly on hardware. When i try to simulate it using simulator it is taking more time than expected.

Say if i make the timer to run for 500mSec then it runs for 4 sec on real time.
So every time it encounters a delay function it is taking more time to execute.

How do i solve this timing issue.

TIA.