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The cited paper doesn't attribute performance variation to silicon to silicon variation. Only the blog post does.
by dchichkov 7y ago
The cited paper doesn't attribute performance variation to silicon to silicon variation. Only the blog post does.
- mlyle 7y agoFrom the abstract: > We show that this variation is further magnified under a hardware-enforced power constraint, potentially due to the increase in number of cores, inconsistencies in the chip manufacturing process and their combined impact on processor’s energy management functionality and recommendations: > • Characterizing node performance based on averaged performance distorts the true impact of manufacturing variation on processors on the node and therefore should be avoided
- rwem 7y agoI wonder how much of this is due to measurement error of temperature. Core frequency and voltage control are governed by some suspiciously round numbers like Tj(max) == 90C. But when the controller thinks Tj == 90C, what's the measurement error?
- mlyle 7y agoA moderate amount. Some of the frequency curve involves the thermal diode, but much less so when TDP capping is used as in the paper. But the temperature of the silicon itself has a lot to do with the performance you get at a given power level.
- dchichkov 7y agoWell, yes, they do speculate in the abstract, note potentially there. It looks like authors do believe the variation is caused by manufacturing variation. But nothing in the paper actually shows it. There's no attempt to determine the cause of observed performance variation in the paper. An empirical survey. Interestingly, that recommendation could be interpreted "empirical studies based on averaged node performance" give a very distorted view on "the true impact of manufacturing variation on processors".
- mlyle 7y agoThe entire study seems to presuppose that most of what is measured is processor manufacturing variation. There's further recommendations about removing the variation with processor binning, etc. It's an interesting set of measurements, but the assumed source of the variation is dubious, and it's not clearly what, if any, actions it really supports.
- dchichkov 7y agoYeah. Maybe authors know something we don't. Or maybe were simply trying to get the paper accepted into a silicon-related conference.