NEED help in upgrading RAM

[vik61]

hi everyone!!!
i am planning on upgrading my memory, right now i have a kingston 4gb ddr3 1333Mhz installed in my pc, and i thinking about adding another 4gb to make it 8gb.
now, should the new 4gb module that i am planning on installing, be of the same company and the same frequency, or can i use another company such as Transcend, and what about the frequency, should it also be the same, i.e, 1333 Mhz???

 

[qwertyDS]

if your motherboard is dual-channel than the memory modules in the same channel have to be indentical in all aspects.

 

[pm4]

Ideal would be to have exactly same brand and model, but you can do also with different brand.
To matter of speed, you should go for same speed for better compatibility. Also if you would use higher for example 1600MHz, motherboard would lower it to match slowest ram in your setup that mean it would be 1333 anyway.

Edit: Risk of incompatiblity is always even with same model bought at same time. That's reason for what they make ram kits, which should be tested together. But generally it should work.