I recently built a new computer, and I'm working with the ASUS P8Z68-V Pro motherboard and Intel i7 2600k processor. While this question does not pertain specifically to my hardware, I mention what I have to explain the voltages/temperatures I get. Do note that the information in your answers should not pertain to my specific case, but computer hardware in general. Furthermore, the information should apply regardless of if the system is under-clocked, stock-clocked, and over-clocked.
In my motherboard, there are two options that pertain to my question. The first is load-line calibration (LLC), and the second is setting the CPU voltage by manual/offset mode. After some experimenting with my manually set multiplier, I have come up with the following as a stable set of voltages in each voltage mode:
- Manual Voltage - 1.19V at idle , drops to 1.18V under load (LLC on high).
- Offset Voltage - 0.93V at idle, 1.19V under load, voltage spikes to 1.25V under load transitions (LLC is off).
Now I understand why the voltages result from each setting (like Vdroop), and why I need to turn LLC on/off in each case, but there are two sides to the hypothetical coin here. While my load temperatures are about equal in each case, the CPU idles a few degrees cooler in offset voltage mode (due to the lower idle voltage).
That being said, in offset mode, I noticed an interesting side effect - load transitioning causes the voltage to spike up to 1.25V. I also noticed that the voltage stays at 1.25V when starting the computer (until Windows is fully loaded and SpeedStep begins to work... brownie points if you can also tell me why this happens). With LLC enabled on any setting in offset mode, the load and idle voltages remain the same, but the peak transition voltage gets a lot higher (over 1.3V).
Conversely, when I set the voltage to manual mode (with LLC enabled, since without it Vdroop causes it to be unstable at idle), the CPU is constantly at ~1.17-1.18V, in both idle/load/startup. My point is that I don't see any voltage spikes between load transitioning - the voltage is almost constant, all the time.
Again, note that in both cases, my load temperatures are the same (a perfectly acceptable 65°C under a stress test, mid to high 50's under normal full load). Thus, I am not worried about temperatures (even at idle), but rather the longevity of the CPU with respect to these voltage settings.
For the long-term use and stability of a computer, with respect to CPU degradation and longevity, is it better to use an offset voltage (which results in a lower idle but higher transition voltage) or manual voltage (roughly constant voltage)? Will the offset voltage spikes (although within my manufacturer's specified voltages) harm the CPU or cause it to degrade faster over time?
Assume the system is under load 60% of the time it is on (which is why I want to use offset mode - cooler and less power at idle).
Reason for bounty: I would appreciate some hard evidence (datasheets, research papers, studies, or any proof really) in favour of one method or another, specifically pertaining to fluctuating versus constant voltage.