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bashcoder | 8 years ago

Alternatively, it could also be in the interest of many for these patches to have an inordinate negative affect on performance with Intel CPUs.

I am reminded that Linus has experience in the CPU industry (Transmeta), so he is in a position to see both sides on this.

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majewsky|8 years ago

Sorta off-topic, but what did Linus actually do back at Transmeta? Did he contribute to their JIT compiler for x86?

FullyFunctional|8 years ago

Probably not secret anymore. CMS (the "Code Morphing Software" that implemented the x86 emulation) originally went straight to translation which was difficult to get correct and was expensive to do for code that might only be run once. Linus, when he joined said "That's stupid" and wrote an x86 interpreter which then acted as the first tier in the emulation. That let to a massive improvement in quality as more workloads could be tested and enabled an awesome creation by Jim Mattson (IIRC): self-cosimulation. CMS could be run in a mode where all translation were cross checked with the interpreter before the results were committed.

This was before my time and I'm sure he did much more. I only have first-hand knowledge of his work on TVM, the Transmeta x86 Virtualization which predated Intel (and AMD's) hardware support for x86 virtualization. Sadly it never productized. I suspect we couldn't find a way to monetize it.

gmueckl|8 years ago

At least the journal reports I read at that time implied that much. He was one of the technical leads on this as far as I recall. So he would have had to get a very good knowledge of the Transmeta CPU and of the x86 instruction set for that task. I think it shows here.