The Itanium architecture is a weird weird architecture. It's not weird in the sense of Alpha's weirdness (e.g., the super weak memory model), which can be fairly easily compensated for, but it's weird in several ways that make me just stare at the manual and go "how are you supposed to write a compiler for this?" It's something that requires a sufficiently smart compiler to get good performance, while at the same time so designed as to make writing that sufficiently smart compiler effectively compiled.

It wouldn't surprise me if Itanium actually had pretty compelling SPECint numbers. But a lot of those compelling numbers would have come from massive overtuning of the compiler to the benchmark specifically. Something that's going to be especially painful for I/O-heavy workloads is that the gargantuan register files make any context switch painfully slow.