I would argue that the shame isn't what Itanium might-have-been, but the architectural roads-not-taken because Itanium absorbed all the resources and mindshare. Would have been interesting to see where Alpha, HPPA...even MIPS R10K family...would be today had the investment thrown away on Itanium been spent more wisely elsewhere.
They'd have been at the same place we are today. CPU architecture is a mature technology and other than horizontal integration and super-wide parallelism, all the basic ideas were already fixed by the early 90's. Those architectures were all just regurgitating each others ideas anyway, there was very little genuine innovation in late RISC.
Well, with the arguable exception of Alpha. The 21264 presaged the modern core most closely, even if it was too big and expensive to be very competitive on desktops. The, er, "21364" reached market a few years later and took over the world as the Pentium Pro.
I generally agree although I do think there's too much mythology around Alpha.
What if Intel had said to HP "That's a really dumb plan" when it brought up the idea of EPIC? I agree probably not much. Intel would presumably have accelerated what Gelsinger called a 64-bit RAS Xeon in a magazine article. Probably good for Intel and not clearly negative for HP. (Both companies went that route in the end anyway.)
Less money would have been wasted in general but it's not like a company spending $100s of millions on Itanium would have told its engineers and other employees to go fiddle with some other exotic architecture. It probably just wouldn't have hired them in the first place.
Seems almost certain that we would have ended up with something that looks exactly like x86_64 a few years earlier in that case, no? I mean, it's not like AMD invented fundamentally new concepts or anything. The doubled GPR set was likely to happen regardless. The REX mechanism might work differently (like moving to a 3-address encoding). Maybe Intel wouldn't have dropped segmentation and we had a new selector record in long mode to worry about. Maybe we wouldn't have the sign bit rule in addresses. None of those are design-breakers.
Again, if no one (including giants like Apple and NVIDIA) has invented new ways to run code in the last 30 years either, it seems like wishful thinking to argue that Intel would have somehow done it had they been less wrong about VLIW.
>Seems almost certain that we would have ended up with something that looks exactly like x86_64 a few years earlier in that case, no?
You're probably right. If Intel had said (internally): "Screw it. Let's just extend x86. It's not like we have anything to fear from AMD." You'd probably have had it a bit earlier. (Though it's not like most buyers of x86-based systems were screaming for 64-bit until into the 2000s anyway so it's not clear that there would have been a big push to pull the timeframes in by much.)
And Intel would probably have still pushed too hard on frequency and ILP--because Microsoft if a senior Intel I exec I knew who isn't prone to lying is to be believed.
Also, yeah. Apple Silicon is great but it's not new paradigm great. If anything, the revolution has been in heterogeneous computing (esp. GPUs to date). And a lot of that has been partly enabled by open source.
That's kind of my point. We didn't need some new, speculative, architectural innovation. We would have been better served investing those Itanium dollars in pushing the mature technology which ran the software we wanted to run better. "Genuine innovation" is often an academic exercise, rather than market changing, though we often don't figure that out until later.
Not sure I'd say the 21364 was PPro since as pointed out it came before 21264. There's clearly some crossbreeding tho. The Alpha bus interface did live on in Athlon, tho.
