I have an i7 2600k, 8 gigs 1600 and HD 5870. With HT on in BF3 i got persistent hitching and stuttering. After I turned it off all was smooth.
I noticed the same type of performance in BF4 but I chalked it up to the updated Frostbite engine and maybe greater system demands because of it. Yesterday I was thinking about it and decided to turn off HT, and low and behold, BF4 responded like a champ. BF4 actually runs better than BF3 did.
So I don't know, is it just my system or is it something inherent in the Frostbite engine that causes this phenomenon on my computer?