Long story short, I recently acquired a free 1 4GB memory stick from a friend through some returns confusion. http://www.newegg.com/Product/Product.aspx?Item=N82E16820231294 I have the 2009 Mac Mini upgraded to Snow Leopard and the original 2 1GB memory sticks from Apple. Should I go with 4 GB or 5 GB keeping a 1GB stick in? My quick investigation suggested if the voltage, timing and latencies were the same, it'd be fine otherwise I should bother. However, I was unable to find this info for my original RAM.