I am building a new pc with 4GB G.Skill f3-12800 4GBRM memory ans Asus p7p55D-E Pro, intel i5-750.
Will I notice a difference in speed with 8GB when using photoshop or opening programs, or having multiple windows open...etc.
4GB is already very decent capacity to start with. 8GB will probably improve the speed but I don't think it will be worth the double the RAM investment as I do not expect double performance.
Whether you go for 4GB or 8GB, just make sure that you got a 64bit OS to maximize you RAM capacity.
Thats what I wanted to hear.
If I add more memory in the future does it have to be the exact same?
I think exact same is not necessity but it is preferable. If in the future, you can not find exact same memory stick as the first two you have, you must get the 2nd pair with the same exact speed rating ( Mhz ) and exact timing as the first set...
Exact same for first set of 2 sticks & exact same for 2nd set of 2 sticks.
The 2nd set is preferable to have same exact speed rating ( Mhz ) and exact timing as the first set... but as others may say, it is not a must. But I really doubt you will need 8GB. Better spend the money on something else like an SSD.