If I can use differernt frequencies of memmory in one machine?

Answer 1

Typically yes, although the memory will only run at the speed of the slowest DIMM. For instance, if you have a stick of 333 MHz memory and a stick of 400 MHz memory, both sticks will only run at 333 MHz.

There is the rare occasion when a picky motherboard will refuse to accept two sticks of RAM that are different sizes and/or speeds, but this is the rare exception rather than the rule.

Answer 2

It's generally a bad idea to mix different speeds of memory. What usually happens is the system treats all the memory as if it was the slowest kind. Not fatal, just a waste of your good memory...

Answer 3

I appreciate kiran's answer it would be better if u get all memories of same speed coz most motherboards either fail to reboot or they consider all as of the lowest speed.