As Raghunathan said, this depends on the crystal used and of course, if there is any logicsoftware that occurs between the consequtive samples.

But, think about it. The standard 8051 takes 12 clocks for each instruction cycle. So at 12Mhz, your able to execute 1 million instruction cycles per second.

So depending on the code, you can do the math and figure the exact number of samples you can take in a second.

Steve