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Athlon 64: How AMD turned the tables on Intel

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331 points giuliomagnifico | 7 comments | 25 Sep 25 18:09 UTC | HN request time: 0.012s | source | bottom
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bombcar ◴[25 Sep 25 18:42 UTC] No.45377061[source]▶
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.

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drob518 ◴[25 Sep 25 18:51 UTC] No.45377177[source]▶
Itanium wasn’t a turd. It was just not compatible with x86. And that was enough to sink it.
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fooker ◴[25 Sep 25 18:58 UTC] No.45377290[source]▶
>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.

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1. bombcar ◴[25 Sep 25 19:07 UTC] No.45377427[source]▶
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.
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2. hawflakes ◴[25 Sep 25 19:27 UTC] No.45377736[source]▶
I lost track of it but HP, as co-architects, had its own compiler team working on it. I think SGI also had efforts to target ia64 as well. But the EPIC (Explicitly Parallel Instruction Computing) didn't really catch on. VLIW would need recompilation on each new chip but EPIC promised it would still run.

https://en.wikipedia.org/wiki/Explicitly_parallel_instructio...

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3. fooker ◴[25 Sep 25 19:55 UTC] No.45378119[source]▶
In the compiler world, these HP compiler folks are leading compiler teams/orgs at ~all the tech companies now, while almost none of the Intel compiler people seem to be around.
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4. hajile ◴[25 Sep 25 20:14 UTC] No.45378374[source]▶
NOTHING produced good code for the original Itanium which is why they switched gears REALLY early on.

Intel first publicly mentioned Poulson all the way back in 2005 just FOUR years after the original chip was launched. Poulson was basically a traditional out-of-order CPU core that even had hyperthreading[0]. They knew really early on that the designs just weren't that good. This shouldn't have been a surprise to Intel as they'd already made a VLIW CPU in the 90s (i860) that failed spectacularly.

[0]https://www.realworldtech.com/poulson/

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5. speed_spread ◴[25 Sep 25 20:55 UTC] No.45378929[source]▶
Even the i860 found more usage as a specialized CPU than the Itanium. The original Nextcube had an optional video card that used an i860 dedicated to graphics.
6. nextos ◴[25 Sep 25 23:18 UTC] No.45380556[source]▶
Yes, SGI sold quite a lot of high-end IA-64 machines for HPCs, e.g. https://en.wikipedia.org/wiki/SGI_Altix
7. jabl ◴[26 Sep 25 10:13 UTC] No.45384790{3}[source]▶
Are you sure about that? If my memory serves, a lot of the Intel compiler people were transferred from HP? At least in the Fortran world, the Fortran frontend for the Intel compiler traces it's lineage back to DEC Fortran (for VAX and later Alpha) -> Compaq Visual Fortran (for Windows) -> Intel Fortran.