Questions about offset mode & LLC for 3770K overclocking.

[PowerK]

Hi guys.

First time posting in AnandTech forums. (But a long time reader).

My setup.
3770K
AsRock Fatality Z77 Professional
4 x G.SKILL ARES 2133MHz (16GB)

I've found a stable overclock for 3770K @ 4.5GHz
Offset = +0.050V
Load-line calibration = Auto (Level 5 which is the lowest/mildest)
All power management options are at default (enabled) (C1E, C3/C6 etc)
Under Prime95 and LinX load, CPU-Z reports 1.200V
This passed 20 passes of LinX and 10 hours of Prime95 (Temps ~ 93C under full load)

I have two questions for those overclocking 3770K.

Now, my questions are :

1. Is it better to *raise* load-line calibration and *lower* offset voltage ?
For example : Offset = +0.040V with LLC at Level 2 ?
Not sure if this would make difference at all since my 3770K seems to require 1.200V under full load to be stable @ 4.5GHz. (Be it with LLC or not, as long as 1.200V is provided to the 3770K, it's the same, right ?)

2. When I went with *Fixed* Mode (rather than *Offset* Mode), below were the value/settings in BIOS which gave 1.200V under full load (according to CPU-Z).
Fixed = 1.215V (BIOS)
Load-line calibration = Level 2 (BIOS)
All power management options are at default (enabled) (C1E, C3/C6 etc)
Under idle as well as Prime95 and LinX load, CPU-Z reports 1.200V
And this gave me BSOD in Prime95 load.
The same voltage was applied to the 3770K. (Offset Mode and Fixed Mode) Why would Fixed mode give me BSOD while Offset Mode goes stable ? (After all, the same amount of juice is provided to the CPU (1.200V)).

Thanks!

 

[Idontcare]

Hi guys.

First time posting in AnandTech forums. (But a long time reader).

My setup.
3770K
AsRock Fatality Z77 Professional
4 x G.SKILL ARES 2133MHz (16GB)

I've found a stable overclock for 3770K @ 4.5GHz
Offset = +0.050V
Load-line calibration = Auto (Level 5 which is the lowest/mildest)
All power management options are at default (enabled) (C1E, C3/C6 etc)
Under Prime95 and LinX load, CPU-Z reports 1.200V
This passed 20 passes of LinX and 10 hours of Prime95 (Temps ~ 93C under full load)

I have two questions for those overclocking 3770K.

Now, my questions are :

1. Is it better to *raise* load-line calibration and *lower* offset voltage ?
For example : Offset = +0.040V with LLC at Level 2 ?
Not sure if this would make difference at all since my 3770K seems to require 1.200V under full load to be stable @ 4.5GHz. (Be it with LLC or not, as long as 1.200V is provided to the 3770K, it's the same, right ?)

2. When I went with *Fixed* Mode (rather than *Offset* Mode), below were the value/settings in BIOS which gave 1.200V under full load (according to CPU-Z).
Fixed = 1.215V (BIOS)
Load-line calibration = Level 2 (BIOS)
All power management options are at default (enabled) (C1E, C3/C6 etc)
Under idle as well as Prime95 and LinX load, CPU-Z reports 1.200V
And this gave me BSOD in Prime95 load.
The same voltage was applied to the 3770K. (Offset Mode and Fixed Mode) Why would Fixed mode give me BSOD while Offset Mode goes stable ? (After all, the same amount of juice is provided to the CPU (1.200V)).

Thanks!

Welcome to the forums as a non-lurker PowerK :thumbsup:

The answer to your first question is that it does not matter how the volts get to the CPU, provided it really is 1.200V, and provided the transients aren't the problem. (CPUZ is going to capture/report the transients)

Another thing to realize about CPUZ and voltage is that is does NOT report the CPU voltage, it reports something that is close to it but is rounded down by a value that can be as large as 0.008V.

Case 1 above could actually be 1.207 being rounded down to 1.200 in CPUZ while Case 2 could actually be 1.200 volts that isn't being rounded at all.

The forumula CPUz uses is the following: (forumla is in Excel notation, if you want to play with it)

CPUz Voltage = ROUNDDOWN((BIOS_Vcc/0.001)/8,0)*8/1000

 

[PowerK]

Thanks for the insight, Idontcare. It feels good to be out in the light after lurking for ten years in this forum! :-D

 

[AkumaX]

Hi, don't mean to thread-jack, but I've got a 3570K, where CPU-Z says the Core Voltage is 1.068V, whether idle or load. This can't be right, right? All settings in BIOS are default.

 

[2is]

You really should start a new thread since its not even along the same topic.

 

[Yuriman]

Hi, don't mean to thread-jack, but I've got a 3570K, where CPU-Z says the Core Voltage is 1.068V, whether idle or load. This can't be right, right? All settings in BIOS are default.

In answer to your question though, some boards have a software layer between bios and windows, making it impossible to see the "real" voltage. What board do you have?

 

[Idontcare]

Hi, don't mean to thread-jack, but I've got a 3570K, where CPU-Z says the Core Voltage is 1.068V, whether idle or load. This can't be right, right? All settings in BIOS are default.

On some mobos, depending on the bios rev, the default settings can end up including the phase mode being set to "extreme" (versus standard or optimized) and/or the cpu voltage mode being set to manual (versus offset).

In those cases the BIOS will not reduce the CPU's Vcc even if the CPU enters a lower power state that would ordinarily include a decrease in Vcc.

(this assumes your BIOS has enabled all the usual cpu power saving states, C1E, etc...if those are disabled then they too will prevent the CPU from receiving the lower idle voltage)

 

[felang]

I've found a stable overclock for 3770K @ 4.5GHz
Offset = +0.050V
Load-line calibration = Auto (Level 5 which is the lowest/mildest)
All power management options are at default (enabled) (C1E, C3/C6 etc)
Under Prime95 and LinX load, CPU-Z reports 1.200V
This passed 20 passes of LinX and 10 hours of Prime95 (Temps ~ 93C under full load)

It used to be that people recommended to disable c3 and c6 when using offset to overclock as it would screw with the voltages a bit, is this still the case?

 

[Kenmitch]

It used to be that people recommended to disable c3 and c6 when using offset to overclock as it would screw with the voltages a bit, is this still the case?

Using offset voltage with c3 or c6 enabled isn't an issue for the most part until you start pushing the clockspeed higher. It may work fine up to 4.5ghz or so but not higher. The real issue is the way the chips vcore isn't really locked to a specific value. It will call for less vcore with a 1-2 core load than with a 4 core loads. Often this results in random bsods doing dumb things like web surfing, email, etc. To get around this you can sometimes just bump the vcore up a little bit. The other option is to just disable c3 and c6 which still allows voltage and speed to drop at idle but under load the vcore is pretty much the same with 1-4core loads.

 

[felang]

Using offset voltage with c3 or c6 enabled isn't an issue for the most part until you start pushing the clockspeed higher. It may work fine up to 4.5ghz or so but not higher. The real issue is the way the chips vcore isn't really locked to a specific value. It will call for less vcore with a 1-2 core load than with a 4 core loads. Often this results in random bsods doing dumb things like web surfing, email, etc. To get around this you can sometimes just bump the vcore up a little bit. The other option is to just disable c3 and c6 which still allows voltage and speed to drop at idle but under load the vcore is pretty much the same with 1-4core loads.

Gotcha... Thanks

 

[PowerK]

It used to be that people recommended to disable c3 and c6 when using offset to overclock as it would screw with the voltages a bit, is this still the case?

In my case, I haven't noticed any difference between C3/C6 on and off in terms of stability. People recommend C3/C6 off for improved SSD performance. But I haven't benchmarked it.

 

[Mike89]

From reading a lot of forum stats on different bios setting results for voltage, you got a low result of 1.2 volts with a +.050 offset. Other results I've seen with people running those kinds of offsets at 4.5 gigs are well into the 1.3s. I used a +.005 offset on my 3770K @ 4.4 gigs and the voltage at load was still around 1.24. My personal goal was to get an overclock of 4.4 gigs (not really interested in going any higher because of the heat and high voltages) at under 1.2 volts at load. I ended up getting my goal with an offset of -.040 and changing the CPU PLL voltage from 1.83 to 1.80. Now I'm running at load about 1.81 v with temps about 63c.