i'll tell you what's wrong, reliability, as i have stated in 3 other posts in this forum, the only place you should buy samsung ram from is newegg. They are the only place that lists the correct model number. All the other resellers either don't list the model number or the model number that is listed is a "customer sample" Maybe it's just me, but i like to get ram that i can trust. Corsair has a lifetime warranty, message boards that are extremely helpful, and they'll send you another one if the stick you have is not performing upto par. Now with samsung, you don't even know what people are giving you, hell it's as if the company is ashamed that it produces ram or something, i've never seen anything so hard to get. Trust me on this one though, either don't buy samsung, or if your life depends on it, buy it from newegg. and for god's sake do some research before you post here, this same question has been asked about 5 times already. All you have to do is visit samsung's site and they have a search engine which finds an exact match for the model number you input. The one you want should say "mass production" not "customer sample" obviously, unless of course you don't mind having a customer sample.