The patent situation is such that one could manufacture a 32-bit x86 processor without the various SIMD and virtualization extensions and not have to worry about patents on the abstract architecture. Implementation techniques up to and almost including the Pentium Pro (November 1995) would likewise be safe from patent threats. However, semiconductors get explicit treatment under copyright law (http://copyright.gov/title17/92chap9.html), so you have to do your own layout until such time as copyrights start expiring again.