> Third, the median processor performance (shown by the green, blue and red lines) between processor 0 and processor 1 on Sandy Bridge show up to 1% difference. However, that difference in median processor performance increases to up to 5% on Broadwell
This socket 1 vs socket 2 variability alone explains 1/3rd of the magnitude of the difference measured in the study-- which makes it quite clear we're not just measuring silicon variability.
The paper itself is pretty clear with the methodology: the throughput of each processor was measured in an installed supercomputing cluster. There are obviously sources of variation in processor performance in a supercomputing cluster beyond the actual silicon plugged into the socket. The experiment has no ability to control for this variation, and no attempt was made.
The reason why we have research and research papers is so we can read about the methodology and think about the limitations of what is measured. It's an interesting measurement that the researchers made in situ; but it also has obvious limitations.
Do we really think that someone who is looking at this type of thing in enough detail to produce the graphs in the article wouldn't think of ambient temperature differential? REALLY?!
Something not being documented well enough for us does not mean that it wasn't considered... Some thing that we thought of going unmentioned does not indicate that said thing was not considered or tried.
This article doesn't mention power supply equivalency or anything about how many people were present in the datacenter during a given test. Here comes the patented HN 'hot take': "uh well actually they don't mention power supplies - are we sure these devices were even powered on?"