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Re:Ampere switching to in-house CPU designs by lmm on Thursday May 20, 2021 @10:37AM (#27221655)
> The compiler also needed to watch the instructions it outputted, as not putting out the right combination of instructions in order would leave CPU hardware underutilized. Instructions were very wide, causing more frequent cache misses as the cache was full of instructions that were shorter in other architectures. Furthermore, the compiler needed to emit certain hints for the branch predictor and other speculative execution units to function well.

I think that's the kind of issue they're talking about. If it had been easier for nerds in bedrooms to run Itanium, we'd've seen much better support for it in GCC etc. much sooner.

Re:Ampere switching to in-house CPU designs by acdha on Thursday May 20, 2021 @11:22AM (#27222329)
I don't disagree with your comment but I think “nerds in bedrooms” is possibly what works for tuning a particular open source project. GCC and other popular open source projects should have been a room full of Intel engineers because it's a hard problem and their revenue from their proprietary compiler & libraries was a tiny rounding error of the amount they spent building Itanium.

Back when I supported computational scientists, the total cost of the servers + compilers was so steep that even if everything had worked as well as the Itanium salespeople promised it would have needed to be many times faster to be worth the hassle of changing toolchains, especially since you had to pay up front for the hope that with a fair amount of work you'd at least hit the point of breaking even.