well amd will void you warranty if you use paste . why they do this i don't know .i think it is because most people use way to much when they apply it . rememeber when you put the heatsink on the fan and put presure on it , it pushes the paste out . the paste it there , or pad , to fill in the tiny little gaps between the heatsink and the die on the cpu . this way it makes better contact . well like i said i think to many people use way to much paste , paste should be damn near seethru when it is aplied . amd cpus have bridges on top of them and maybe amd feels that the excess paste will touch them and either curode them or cunduct and fry the cpu . thats my guess and thats all it is so don't take it for fact please

but if you go to amd site it will tell you that u must use amd aproved pad for the warranty to be valid . i think it even says it on the paperwork you get with the retail box version. there is a thermal pad on the bottom of the hs that comes with the retail cpu . so just use that and you will be fine . and as long as you aren't overclocking and you have good air flow you will be fine . people say 50c is to hot but there operating temp is up to 70c so 50 is fine .
the only reason i can say why people buy oem is to save a few bucks is all . at one time oem were alot cheaper that retail but today the difference is only a few dollars . i have been building my own pc's since the mid 90's and i have never had to use the waranty for a cpu . and in that time i have only fryed one and it was about 2 years ago trying to be fast . also with the price of cpus today , well if you buy in the middle of the curve like i do it is almost more hastle to rma a cpu to either vendor or maker . i just get a new one , time is money and if my pc is down i am pissed . it cost you money to shi back and wait for them to say ok we will send you another or no you voided the warranty . but like i said i have never had a cpu go bad on me and i doubt that maybe have to be honost . most dead pc's are from operator error not defect . so i don't worry about the warranty on a cpu . but thats me .