Adding Different frequency RAMs

[dpnshu.kmr]

My acer aspire e1-571 is already having 2GB, 665MHz, DDR3, single channel, 1.5V RAM as found by Speccy, CPU-Z and my own info. Can i add 4GB, 1600MHz, DDR3, bidirectional, 1.5V RAM into another free slot? Answer asap. Thanks

[DaveLembke]

Your DDR3 RAM that you see as 665 mhz is likely 1333Mhz DDR3. You can mix with 1600 Mhz RAM in most situations the RAM will down clock to 1333Mhz. Some RAM doesnt like to play well with others. So there is the slight chance it wont work. Its always best to match RAM speeds and brands and sizes when possible, however for years I have mixed RAM sizes and speeds and you just need to know that the RAM will downclock to the slowest stick added. If your buying RAM, I would go with 1333Mhz to match, but if you acquired some 1600Mhz DDR3 cheap or free then give it a try and see what happens. After mixing memory I would run memtest86 to make sure that the system is truly happy with the mixed RAM.