What kind of RAM do I need for a Sony Vaio PCV-RX540 ?

Answer 1

Go to www.crucial.com (a memory manufacturer) and use their Memory Advisor Tool. You select your computer's brand, model, etc. and they tell you exactly what to order.

There are lots of different models, but there are subtle differences, so don't order anything just because it looks "close". Although some of the "close" ones will work, sometimes small differences will make big differences in performance.

It's better to spend a few extra bucks for something that is an exact match for your pc. It will last a long time!