Azul Systems has asked Intel to do this once... but instead created their own processors with interesting memory barrier properties for awhile that greatly sped up JVMs beyond what was capable (at the time) on x86-32/ppc/sparc. Eventually they gave up and became a purely software company, but their "Java Mainframe" product was many times faster than the Intels of the age executing the same code despite much slower CPUs. Died a quick life despite the cool factor.
