Memory speeds and compatability
Memory is designed to be backward-compatible, so generally speaking, you can safely add faster memory to a computer that was designed to run slower memory. However, your system will operate at the speed of the slowest memory module.
One thing to keep in mind is that the memory does need to be the same type - for example, SDRAM cannot be mixed with DDR, and DDR cannot be mixed with DDR2 and DDR2 cannot work in a DDR3 system.
We recommend that you use the Crucial Memory Advisor™ or System Scanner tools to find the right memory for your computer. Rather than give memory modules catchy names, the industry refers to modules by their specifications. But if you don't know a lot about memory, the numbers can be confusing. Here's a short summary of the most popular types of memory and what the numbers refer to.
DDR3 memory is the latest generation of memory for computing applications and offers many benefits over DDR2 including lower latencies, higher speeds, and more.