Can i put a combo of 2 different companies with the same speed?

How do the voltages and latencies compare?

dunno. i found corsair at fry's and a-data are 1.5v. my friend has corsair memory (i helped him to build it, so i know his parts). if you need it, i can ask him

so, hello, anyone, please? should they be the same? or it's ok if their latencies and voltages are different? what's the limit?

You should have simillar voltages and timings..

If you post specifications on your current ram along with specifications on your new ram it will be much easier to help you. By specifications I mean default voltages, timings (CAS-tRCD-tRP-tRAS), memoryspeed(PC3-12800, PC3-10600 etc etc) , article number. These numbers are found on your hardware cases or if you ordered them online they are found together with your ordernumber in your emailbox.

Which motherboard do you have, and which memoryspeeds is it compatible with?

Though if you only have 2x1gb ram to begin with, id remove it and buy a new pair, unless you can find your old memory to a reasonable price. 4gb is more than enough in most cases.

i'm getting 2x2 gb corsair, and 3x2 gb A-DATA. both are 1333mhz. i don't know the timings and voltages. but i'll keep that in mind. thank you. motherboard will be (i think, if the second is better, please tell me) Asus P7P55D-LE (supports 1066-2000 mhz). or the second one (though i think it's worse) gigabyte ga-p55-us3l (supports 800-2200)

so, if i understand it correctly, i can use 2 different combos as soon as they have the same speed (in mhz), voltages and timings, right?

You're buying 10GB of ram? That's overkill, even 8GB seems overkill to me. You would be PERFECTLY FINE with just the A-Data 6gb kit. I would just make sure that they have heatspreaders on the memory sticks themselves incase you want to do any overclocking.

no, i'm just buying one kit so far. the only problem is that i want to try the UDK program, which requires for the "full speed" 8 gigs... or 4 gigs would be ok? http://developer.nvidia.com/object/udk.html

I couldn't find any page that listed the requirements for that program, could you link me to it? I'm sure 4 gigs would be okay. What processor/motherboard type are you getting? Because you need to know what type of RAM to get, Triple Channel or Dual Channel.

With triple channel, I think you need GB's in multiples of three (3gb, 6gb, 9gb, etc. Please correct me if I'm wrong) and with dual channel you need GB's in multiples of two (2gb, 4gb, 6gb, 8gb, etc. Again, correct me if I'm wrong.)

ok, so i found it... http://udk.com/download.html and i don't know about 3channel, but with 2 channel it's 2, 4 and 8. no 6gb (or at least if you're crazy you can get 2x2 and 2x1, in which i don't see a big idea.