DDR2 VS DDR3 performance

DDR3 certainly does offer a significant performance increase over DDR2: double the memory bandwidth and much faster speeds. However, whether you see any kind of benefit is very much determined by how powerful your other components are. Could you please post a complete list of your specs so we can check that a RAM upgrade wouldn't be bottlenecked by other components?

To be honest, the performance difference will be minimal as they both are double data rate. You may see a slightly larger increase if you install 8GB and run a 64-bit OS.

DDR3 memory is only supported by installing AM3/AM3+ CPU; I presume that your CPU meets the specs.

http://www.tweaktown.com/articles/1782/amd_phenom_ii_dd...

i have Phenom II x4

That CPU supports DDR3, but what are your performance improvement expectations?

Did you read this article? http://www.tomshardware.com/reviews/phenom-ii-ddr3,2319... You can ignore the meaningless synthetic benchmarks, but the games and applications that you use are a good reference. Presume that DDR2-800 and DDR3-800 performs the same.

DDR3 is not that much faster than DDR2

DDR3 1600MHz CAS 9 9/1600*2000 = 11.25ns
DDR2 800MHz CAS 5 5/800*2000 = 12.5ns

Realistically you wont see that big a difference. Your main issue is that you have 3GB. that means you cant be running in dual channel mode.
How are you configured ?

This is how I see it.
If you have 3 1GB strips put them to one side as spare's and get 2 x 2GB DDR3 1600 strips and put them in dual channel mode.

If you do have a 2GB DDR2 strip then check the price for a second strip the same to put with the one you have in a 2 X 2GB DDR2 set up.
I have not checked prices for a good while now but you could well find that its going to work out cheaper or not that much more expensive to go with a 2 X 2GB or even a 2 X 4GB DDR3 1600 set up.

Mactronix  

i have 1gb+2gb 800

Ok well check prices local to you and see if its better to go 2 X 2 GB DDR2 or if its not that much dearer switch to DDR3 either 2 X 2 or 2 X 4 depending on price and budget.

Mactronix  

8GBDDR3<>8GBDDR2>6GBDDR3<>6GBDDR2>4GBDDR3<>4GBDDR2>2GBDDR3<>2GBDDR2 Who cares what DDR you have. 8GB RAM is good enough for everything.

Don't be so ignorant. Running Photoshop and Illustrator simultaneously definitely benefits from having 16GB of RAM.