Laptop RAM

I have an IBM laptop (specs in my sig) that has 256 of PC2100 RAM. I want to add another 512 stick, but if I buy anything higher than 2100, does it operate any faster, or do both sticks run at 2100?

If your motherboard is limited to 2100, than that's as fast as it'll go, regardless of the RAM speed.

I'll have to check the limit. If it is 2700 though, what happens if I have a 2100 AND a 2700? Does it run at 2100 only?

Edit - It's only 2100, so my question is pointless now.

Thanks anyways.