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by lmm 433 days ago
> CPUs get microcode updates all the time, too.

To fix bugs, sure. They don't generally get updates that contain new optimizations that radically break existing machine code, justifying this by saying that the existing code violated some spec.
1 comments
carlmr 433 days ago
>To fix bugs, sure.

Maybe your program worked due to the bug they fixed.

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lmm 433 days ago
Extremely unlikely. CPU bugs generally halt the CPU or fail to write the result or something like that. The Pentium FDIV bug where it would give a plausible but wrong result was a once in a lifetime thing.
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baq 433 days ago
Spectre and Meltdown exploits stopped working, too. Some of them on some CPUs, anyway.
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lmm 432 days ago
Sure. But those were obviously exploits from the start. You wouldn't write code like that accidentally.
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ryao 433 days ago
Do a web search for rdrand and systemd.
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lmm 432 days ago
> Do a web search for rdrand and systemd.

RDRAND always returning all-FF is exactly the kind of thing that's an obvious bug, not a plausible-but-wrong result.

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ryao 432 days ago
The other guy said "Maybe your program worked due to the bug they fixed.". The RDRAND fix achieved exactly that.
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