Outstanding article! Thank you, Paul! I would love to have been there. I have a few dozen questions that the Team may or may not have been allowed answered.
However, like
bit_user, I found it of particular interest that the Team was forthcoming regarding specific voltage and temperature values they're comfortable with running on their personal home rigs, which max out at 1.425 and 80°C. With respect to electomigation and longevity, every day in the forums we see many overclockers express their concerns over these very issues.
On their website,
Silicon Lottery shows Historical Binning Statistics that include the Core voltages used to validate their overclocked 14 and 22nm processors. For 22nm the maximum is 1.360. For 14nm the maximum is 1.456. While Intel's warranty is 3 years, Silicon Lottery's warranty is 1 year, which suggests at least one reason for the voltage difference between Intel's Team and Silicon Lottery.
Here's a forgotten link to a revealing Tom's Hardware video interview of July, 2016, with Intel's Principal Engineer (Client Computing Group), Paul Zagacki, where
Intel Discusses i7-4790K Core Temperatures and Overclocking. The video coincides with the formation of Intel's Overclocking Lab, also in 2016. In the video, Intel points out that overclocking abilities begin to "roll off" above 80°C, which agrees with the value the Team revealed in your article.
While Core temperatures, overclocking and Vcore are often highly controversial and hotly debated topics in at least the overclocking forums, the term "
electromigration" is closely related to a much less known term, which is "
Vt (Voltage threshold) Shift". With respect to voltage and temperature, the two terms describe the causes and effects of processor and transistor "degradation" at the atomic level.
In the
Intel Temperature Guide, in
Section 8 -
Overclocking and Voltage, I created a table for
Maximum Recommended Vcore per microarchitecture from 2006 to the present. For 22 and 14nm, those values are 1.300 and 1.400 respectively. I also created a graph showing the
Degradation Curves for 22 and 14nm processors. The table and graph helps overclockers get a better perspective of the degradation and longevity issue:
Sparing our members and visiting readers the deep dive, Vt Shift basically represents the potential for
permanent loss of normal transistor performance. Excessively high Core voltage drives excessively high current, power consumption and Core temperatures, all of which contribute to gradual Vt Shift over time. Core voltages that impose high Vt Shift values are
not recommended. The 14nm curve suggest 1.425'ish is the practical limit, which also agrees with the value the Team revealed in your article. The curve also suggests that Silicon Lottery might be pushing the edge of the envelope a bit.
The concern here is that when novice overclockers casually glance around the computer tech forums, where conflicting and misleading numbers get flung around like gorilla poo in a cage, many don't realize through the fog of all the confusion that one size Vcore does
not fit all. Aside from high Core temperatures, Vcore that might be reasonable for one microarchitecture can degrade another. So 22nm Haswell users now wanting to overclock their aging processors to keep up with today's games need to heed the degradation curves, which applies as well to 14nm Skylake and Kaby Lake users.
CT
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