[citation][nom]cookoy[/nom]Between the time of the filing and the time the patent got approved (let's just say April 2007 to Feb 2012), if AMD came out with something similar in their cpu design, did AMD violate Intel's patent? Like a crime is breaking the law and if there is no law then there is no crime. You can't apply the law retroactively. Any legal experts out there to enlighten us on this?[/citation]
Under current US patent law, priority is awarded to the 'first to invent' something. So in order for AMD to prevail under your scenario above, they would have to demonstrate that they conceived and reduced to practice the claimed invention before Intel did. To show prior conception, they would have to have lab notes and other written evidence predating Intel's, showing that they thought of the idea before Intel did.
Usually the first to file a patent application on the idea is taken as constructive reduction to practice. However if AMD could show they were diligently (i.e., no long breaks) working on the invention, they could supercede Intel in what is called an interference proceeding and be awarded priority.
However under the American Inventor's Act, which goes into full effect this year IIRC, US patent law is being harmonized with European and Japanese patent law, which awards priority to the first to file a patent application. So that means if you file an application first, you are automatically awarded priority no matter how much work the competition can show they did before you filed, or did for that matter.
However I also think that AMD & Intel have a cross-licensing agreement in effect which may mean that AMD gets to use Intel's patents in exchange for the X64 patent that belongs to AMD. Not sure of the particulars of that agreement, so I dunno if it covers new stuff like this. But, if true, then this patent would deter somebody like ARM if they wanna get into hyperthreading and use the same or not-patentably-distinct (obvious) variation on Intel's patented technology, whereas AMD would not have to worry about it.