Patents are what are generally what is used by Intel, etc to protect (and license) new CPU instructions and provide protection for novel ideas/inventions for up to 20 years.
Copyright generally protects specific expressions/implementations of an idea and last up to 95 years for corporate patents, or 70 years + the lifetime of the author for individual patents.
For completeness there is also trademarks which cover names and logos which can last indefinitely, as long as they are in commercial use.
The text of a CPU instruction specification would be covered by copyright, the algorithm for implementing the instruction by a patent, and the branding (ex: MMX) by trademark.