So my Vcore as logged by HWmonitor is 1.41 max and I think that's high (most people do). It normally sits at 1.35 in load but can spike up, and at idle its 0.928 or something. But, I went to my BIOS and switched my Vcore from Auto to 1.35. The problem with this is that I would still like it to lower to sub-1V when idle.
Is there a way to allow it to lower but force it to a 1.35 max?
There's a couple of things about vcore:
- Vdrop: every mobo has vdrop. The vcore you see in cpu-z will always be a little lower than what you specified in the bios/uefi. Some mobo's have worse vdrop than others.
- Vdroop: this is an intended mechanism as specified by Intel. Simply put, it adjusts the vcore under load in order to prevent damage by short voltage spikes that might occur when switching to load state. In cpu-z you will see the vcore fluctuate during load.
Vdroop makes overclocking harder. The difference between the lowest and highest vcore value will grow when you increase vcore in bios. Lets say at stock, vcore under load is between 1.2 and 1.1V. If you increase vcore it might become 1.4 and 1.2V. So the difference between the highest and the lowest value has increased from 0.1V to 0.2V.
Suppose your cpu at a certain frequency needs a minimum of 1.3V to remain stable. As you can see the highest value of 1.4V is plenty but the minimum of 1.2V is too low. So you will need to increase vcore more, which will make the difference even bigger. You might need 1.55V to ensure a minimum of 1.3V. My numbers are exaggerated to make the example more clear but this is what you are noticing in HWmonitor.
To make overclocking easier most mobo's have a Load Line Calibration or VDroop option. This option enables or disables the Vdroop mechanism. With LLC enabled you will see no more fluctuating vcore under load, or just very slightly.
There's some debate about wheter enabling LLC has harmful effects. I wouldn't be too worried about it since there are many overclockers using it and running their cpu's fine for years. The alternative isn't very attractive. With vdroop enabled you'll need to overcompensate on the vcore causing high spikes. On the other hand, if your oc stays stable within safe voltage margins with Vdroop enabled, I see no reason to disable it.
- C1E/EIST: both these technologies lower the vcore and multiplier in idle. The difference is that EIST can adjust the multiplier and vcore according to load (fex. only x25 with 1.1V under light loads while the max would be x30/1.2V), whereas C1E will always use the highest multiplier and vcore, light or heavy load.
Both C1E and EIST can only lower the vcore in idle if it is set to 'auto' or using an offset/dynamic mode. If you set the vcore to a fixed value EIST and C1E will not lower it in idle.
The problem with 'auto' is that mobo's generally apply way too much extra voltage when increasing the multiplier or bclk. Therefore auto isn't very usefull for overclocking.
Most mobo's (except MSI afaik) nowadays have a dynamic vcore option. You can lock the vcore to its standard values and specify an offset value, either positive or negative. Now C1E and EIST can lower the vcore in idle even when overclocked.
However, altough a nice feature, dynamic vcore is not completely necessary. There's a third power saving mechanism called C-states or C3/C6, which basically turns off the cpu even more than C1E. If you leave C-states enabled idle power consumption will be about the same regardless of lowered vcore or not.
It would be interesting to learn if C-states cause any instability at all when overclocking SB.