Patents are odd things. Digital (DEC ever heard of them?) Came up with one of the first patents for parallel computing on a CPU, In 1997 intel bought a license from Digital for the technology, and hired a lot of their Digital employee's to develop Hyperthreading.
Thats why the P4 designed in 1998 included Hyperthreading from day one.. just disabled as in Willemotte's initial (2000) form it didnt work very well.
So while its true AMD did take out a patent in 2002 odd, there was already a previous patent registered covering the same basic concept. I cant find what year Digital registered their patent, but intel licensed and developed what was probably the first 'working' Hyperthreading processor.
Digital themselves were bought up by Compaq in 1998, no clue who now owns the patent, but intel can use the technology based on their 1997 license.
Another company 'MicroUnity' also claim to hold the patents for Hyperthreading.. Oh what a twisted web of papers. They tried to sue Intel for Hyperthreading, and SSE. This company was only formed in 1998, so how they can claim to have a patent infringement on something intel licensed in 1997 is unclear, but then im no legal expert... Infact I'd say the USA's biggest downfall is everyone sueing everyone else. Only people that benifit are the lawyers.
Kinda funny have a loose 'vague' statement, which encompasses a good idea, can become a patent long before any 'actual' designs or technology even exist to make it possible.
Seems to me, that half these 'patent' claims come about because original patents were badly worded, and some bright spark (lawyer) looks at a technology like Hyperthreading and makes a far more 'accurate' description of it, and then registers it as a patent!
Oh as for X86 technlogy, it's still intels baby, but IBM forced intel to allow AMD to manufacture processors, so that they didnt have all their eggs in one basket. Over the years the deal between AMD and Intel has changed, with both party's sueing each other. Until finally just after the 486 was released, they both sued each other one more time, both winning LOL, and then they signed the aggrement they have today, which pretty much allows both parties to work on virtually the same technologies without major risk of being sued. Thats why AMD are even allowed to make X86 processors, and its also why intel were allowed to use AMD's own design notes to implement EM64T.
Its a good thing really, would be a nightmare if the two companies continually released incompatible processors. Imagine AMD without SSE1/2/3/4, MMX, or to be honest, even 486 microcode. Likewise Intel got to make use of AMD's work extending the X86 platform to 64bit... We're the winners on this one.