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So if I understand this right, CPUs try to predict what operations are going to be made in order to gain performance, but instead introduced a vuln that killed
by Popegaf 5y ago
So if I understand this right, CPUs try to predict what operations are going to be made in order to gain performance, but instead introduced a vuln that killed performance? Wouldn't the logical thing be then to get rid of the predictions on hardware in order to be able to turn off these mitigations?
Are there CPUs out there / being made without these SoC predictions?
- dkarras 5y agoI'm not sure if I got you right: The performance boost with speculative execution is massive. It introduces a vuln. It is the fix for that vuln that kills the performance.
- Popegaf 5y agoWhat I'm saying is if the fix for the vuln negates the performance boost from speculative execucution, then the net outcome is 0 performance boost and speculative execution might as well be removed entirely. It wouldn't surprise me if it just costs more energy to keep the vuln and mitigation active at the same time.
- SAI_Peregrinus 5y agoThe fix doesn't negate the performance boost. It decreases it. But it's still nonzero boost.
- p_l 5y agoThe techniques used to make CPUs fast have possible vulnureable areas (not all of it is due to Out-Of-Order Execution, some was due to optimizations made on top). The mitigations introduced stalls into those mechanism, clearing some of the state, resulting in slowdowns. However, the mitigations are not as big slowdowns as not having the speculative execution mechanism at all.