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by jacques_chester
4807 days ago
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IA64 was an entirely new instruction set on an entirely new architecture; having nothing whatever to do with x86. Compatibility for x86 was added later to try and improve sales. AMD64 / x64 pretty much hops into a different mode and goes on executing from there. Given how many modes and instructions these chips support, I don't see why adding another would easily upset people. |
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However there is a big difference: the move to 64-bit words was something that was in demand when it was introduced. There was a market for it, with a very clear value proposal.
In contrast a new "mode" with the same computational power plus dataflow annotations would be a tough sell: larger code size, and and better performance / watt only for some applications.
(Also, as far as I know AMD64 / x64 on Intel cores uses the same decode and issue unit, just with different microcode. Circuit-wise there is a lot in common with x86.
Here we would be talking about a new mode and also a new instruction+data path in the processor. The core would become larger and more expensive. Not sure how that plays.)