Upgrading from 4GB to 6GB RAM, questions.

Originally Posted by byteninja2 

Well, about a %50 chance the Memory will not run dual channel. Honestly, the 2 GB would not be worth it. Get 2 more 2 GB samsung sticks or another 4 GB stick.

Originally Posted by lightsout 

Unless your maxing your ram and need it for a particular situation. I also say don't bother. I bet it will probably run in dual channel fine. Ram is way cheap over here. PayPal someone some money and have them get you a nice cheap 8gb kit and mail it to you.
I'd be willing if you are so inclined. Good luck

Originally Posted by jrbroad77 

I've run a couple of laptops with 6GB of DDR3, sticks were the same speed but different brand and it does run in dual-channel. The worst that can happen is, if the timings aren't matched, the faster stick will run at the slower timings (same 1333mhz though).
The confusion of running 2 sticks of a different size in dual-channel can be cleared up as follows-
If you have 2 sticks the same size, each one gets filled with half the data.
If you have 2 sticks, different size: Each gets filled with half the data, until the smallest stick gets filled. Then the larger stick gets filled with the remaining data. So once you go past 4GB of RAM usage, the remaining RAM will be read at single-channel speed. Anything in the 1st 4GB will be read at dual-channel speed. The OS takes care of the memory addressing, so you don't have to concern yourself with how Windows knows whether to read from both sticks for a piece of data, or from just one
Now, I'm not sure if the OS is completely loaded onto the larger stick, but that would seem more efficient to me- OS doesn't need a ton of speed (of the 1GB that W7 uses, you're not going to do a ton of memory read/writes - I benched my dual-channel 8GB DDR3 at about 3GB/s, single-channel would be 1.5GB/s.. no way an OS would need 3GB/s), at least compared to some more intense programs.
At any rate, adding a 2GB stick will increase your bandwidth, even if you only need perhaps 4GB of RAM. It'll show up in synthetic benches, and probably in a couple of games, by a couple FPS here and there.

Originally Posted by kz26 

Theoretically, there's a small chance that the sticks may be incompatible, although in recent times I haven't had any issues mixing and matching different DIMMs.
All recent Intel CPUs support Flex Memory Technology, which allows the highest matching capacity (i.e. the first 2GB) to run in dual-channel mode, and the remainder running in single-channel mode.