Itanium failed in the market because it wasn't fast enough running general purpose code (HPC workloads were a different story). As a consequence, it's ability t

Itanium failed in the market because it wasn't fast enough running general purpose code (HPC workloads were a different story). As a consequence, it's ability to run existing x86 code was poor (both in hardware and software emulation). At the root, Itanium's poor performance was a direct consequence of the design assumption that a sufficiently smart compiler could extract sufficient instruction-level parallelism. While the ISA didn't prohibit later improvements like OoO execution, it always required a better compiler (and more specific workloads) than real users would have.