alt_timestamp timer information

Hi,

I am using the interval timer for my design. Below is part of C code I used. The elapsed time I am getting is around 1000 ticks. I have this doubt that this part of code will take 1000 cycles to run or am I doing something wrong? Also, I would like to know what is the difference between performance counter and interval timer when it comes measuring the time elapsed?

if ( alt_timestamp_start() < 0 )

{

printf("No timer devices available.\n\n");

}

time_elapsed = alt_timestamp();

printf("Time elapsed %ld\n\n", time_elapsed);

Thanks.