Athlon 64: How AMD turned the tables on Intel

Youngsters today don't remember it; x86 was fucking dead according to the press; it really wasn't until Athlon 64 came out (which gave a huge bump to Linux as it was one of the first OSes to fully support it - one of the reasons I went to Gentoo early on was to get that sweet 64 bit compilation!) that everyone started to admit the Itanium was a turd.

The key to the whole thing was that it was a great 32 bit processor; the 64 bit stuff was gravy for many, later.

Apple did something similar with its CPU changes - now three - they only swap when the old software runs better on the new chip even if emulated than it did on the old.

AMD64 was also well thought out; it wasn't just a simple "have two more bytes" slapped on 32 bit. Doubling the number of general purpose registers was noticeable - you took a performance hit going to 64 bit early on because all the memory addresses were wider, but the extra registers usually more than made up for it.

This is also where the NX bit entered.

Itanium wasn’t a turd. It was just not compatible with x86. And that was enough to sink it.

>Itanium wasn’t a turd

It required immense multi-year efforts from compiler teams to get passable performance with Itanium. And passable wasn't good enough.

Wasn't the only compiler that produced code worth anything for Itanium the paid one from Intel? I seem to recall complaining about it on the GCC lists.