I am upgrading my desktop, I purchased an ASUS P5G41C-M LX motherboard and I’m thinking to get CPU: Core 2 Duo E6400. I will put 2 x 1GB dual channel memory. My question is what dual channel memory should I get - the best bang for the buck? Should I get DDR2 800, DDR2 1066, DDR3 1067 or DDR2 667 - will do just fine? Do I have any performance gain if I buy the DDR3 memory? The motherboard supports both DDR2 and DDR3.
DDR3 1066 memory will perform worse than DDR2 1066 memory. You need the faster speed to make DDR3 worthwhile.
In all honesty, get the cheapest. Ram has the absolute lowest performance gain per increased cost in practical usage; even benchmarks show relatively little performance increase from one speed to the next. You would be better off with more memory than less and faster memory in 95% of circumstances.
That said, I would get DDR3 1333MHz for several reasons:
-currently the same price as DDR2 memory
-will hold it's value longer and you could reuse it in a new system build up to possibly 3 years from now
-As much as I said speed doesn't make much practical difference, I just hate the sound of DDR3 1066. Plus, you would be hard pressed to find DDR3 1333 memory more expensive than DDR3 1066 memory. Just like you would be hard pressed to find DDR 667 memory for a lower price than DDR2 800MHz memory.
The E6400 Conroe core (if you found one of these it's pretty old) has an FSB freq of 266 MHz. Allowing for overclocking, the DDR3-1333 is probably at the sweet spot.
The E6300 or E6500 Wolfdale CPU's also have a 266 MHz FSB freq, but they run at 2.8 and 2.93 GHz, respectively. The much greater speed more than makes up for the smaller cache. And they are much better values than the Conroes.
Even on a G41 motherboard, you should be able to reach 333 MHz FSB. That will do two things: run DDR3-1333 RAM at its full rated speed and give you a core speed of around 3.5 GHz.
In fact, I have a system that I put together out of leftover parts and an E6500. It's running in a Gigabyte G41M-ES2L motherboard with 4 GB of DDR2-800 RAM. It's Prime95 stable at 3.63 GHz (333 MHz X 11).
Based on a sample of two G41 boards (yeah, big statistical sample ), you cannot push the G41 FSB higher than around 365 MHz.