Hi, i have DDR2 2x1GB of OCZ 800Mhz memory on Gigabyte P35C-DS3R motherboard also i have ATI 4870 graphic card and 23inch lcd. And now i want to upgrade my PC to 4GB of DDR3 1333Mhz, because i want to play some new games on top guality settings.
And now im asking if there is major difference betwen DDR2 2GB 800Mhz (5-5-5-15)and DDR3 4GB 1333Mhz(6-6-6-20). I will be playing games on 1920x1080 resolution.
The RAM that im interested in is this- http://www.ocztechnology.com/products/memory/ocz_pc3_10...
You'll need a new board for the upgrade. If you want to get 4 gb anyway, ddr3 is a good choice. I would sell your old board and ram on craigslist. Speed difference may be only 10% overall when the quantity is the same. Could be more if the new board overclocks well.
Since your motherboard supports both DDR2 and DDR3, you won't need to upgrade as o1die says.
The DDR3 RAM is a little faster (1333MHz vs. 800MHz) which will increase performance slightly.
Most of your performance increase will be due to the larger amount of memory, more so than the slight increase in speed (i.e. Windows will have more room for system stuff and won't interfere with your games own memory reserves).
If you could find a DDR2 2x2GB kit for cheaper than the DDR3 kit, it could be worth it (considering you don't plan to upgrade the rest of your computer in the near future). However, if the DDR3 kit is a good price, I don't see any reason not to go with more memory.
You should definitely see an improvement with the increase in storage space, and if you do upgrade your computer (to, say, a Core i3/i5/i7), the DDR3 memory will still be useful (unlike DDR2 memory which Intel no longer supports with its top processors).
EDIT - One other option might be to just buy a second set of 2x1GB DDR2-800 memory. It wouldn't be much slower than your current setup (some penalty for all 4-banks, but not much), and the performance boost from additional memory is still there. But remember, DDR2 is being phased out, so in the long run, you might just be stuck with 2 more sticks of DDR2 you can't use. Its up to you.