Comment by bombcar

5 years ago

Nowadays there’s hardly a device that can’t easily be updated after shipment - so the cost and effort required to make a perfect error-free CPU is not as incentivezed.

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bombcar

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jeffbee  5 years ago

The updates are often fatal, though. These include things like the Opteron "Barcelona" TLB bug and the first-generation EPYC "Naples" frequency scaling bug. The fix for the former knocked 20% off the performance of that generation of parts, and the fix for the latter meant that you had to run at the base clock frequency at all times, getting neither turbo boosts nor power savings. If you apply all of the speculative execution workarounds to an older Intel part like Xeon E5 v3 you will lose something like a quarter of the performance you paid for originally.

  • bombcar  5 years ago

    Yeah, I was thinking more of architecture errors where the solution is “modify the compiler so that code isn’t called” - though some may allow microcode updates.

    The various spec-ex workarounds actually matter more on things like cloud servers than they do on dedicated/controlled hardware.

amelius  5 years ago

> Nowadays there’s hardly a device that can’t easily be updated after shipment - so the cost and effort required to make a perfect error-free CPU is not as incentivezed.

This ignores the fact that there can be security exploits.