Hi Prad,
What mechanism are you using to measure the timer time delay? Are you measuring the time between two consecutive Hwi's? Are you toggling a GPIO and seeing the output on an oscilloscope?
SYS/BIOS will add some delay from the time a timer Hwi is triggered to when a Hwi function is running (thread safety & context switching requirements). But the delay should be in hundredths of microseconds not milliseconds. Do you have any other high priority Tasks or Swi's running while you are performing your measurements?
Regards,
-- Emmanuel