safe Vcores?

[Proprietary]

Do safe Vcore numbers change with different CPUs? I've heard that 1.4v should be the maximum Vcore, but would that number be lower with an older CPU? 

[JoostinOnline]

It depends on the architecture. 1.4V is way past what's considered "safe" for most CPU's. What model do you have?

[Proprietary]

1 hour ago, JoostinOnline said:

It depends on the architecture. 1.4V is way past what's considered "safe" for most CPU's. What model do you have?

I don't have a specific model in mind... just wondering in general, but an amd threadripper can reach 1.4v, right?

[KarathKasun]

3 minutes ago, Proprietary said:

I don't have a specific model in mind... just wondering in general, but an amd threadripper can reach 1.4v, right?

You will be pumping out enough heat to cook your dinner at 1.4v on TR.

 

Expect 1.3v on new threadripper with extreme cooling.  If they do a 64 core TR-3 you would be looking at 600w+ for the CPU alone at that voltage.

[JoostinOnline]

6 minutes ago, Proprietary said:

I don't have a specific model in mind... just wondering in general, but an amd threadripper can reach 1.4v, right?

You'll probably damage your CPU by pumping 1.4V into it long term. For TR people usually use less than 1.35V. Voltage isn't something you want to increase unless you have to.

[Proprietary]

11 hours ago, JoostinOnline said:

You'll probably damage your CPU by pumping 1.4V into it long term. For TR people usually use less than 1.35V. Voltage isn't something you want to increase unless you have to.

Why is pumping extra voltage so dangerous anyways? If my cooler is powerful enough, can I theoretically increase the vcore infinitely?

[fluxdeity]

12 hours ago, JoostinOnline said:

You'll probably damage your CPU by pumping 1.4V into it long term. For TR people usually use less than 1.35V. Voltage isn't something you want to increase unless you have to.

It's not voltage that kills, it's amperage and temperature. If you can adequately cool 1.5v below 40-50C it's relatively safe. On Ryzen chips you can safely run 1.4Vcore 24/7 for overclocks. If you look at stock voltage is can spike to even 1.5v, while it doesn't hold it there for long, it still hits it.

[Falkentyne]

14 hours ago, Proprietary said:

Do safe Vcore numbers change with different CPUs? I've heard that 1.4v should be the maximum Vcore, but would that number be lower with an older CPU? 

Based on *AMPS*.

1.520v is the absolute MAXIMUM safe vcore provided NO AMPS are going into the CPU, based on using Intel defaults of a 1.6 mOhm VRM Loadline.  Meaning the CPU must not be subject to a clock signal if this is actually the VCC_Sense voltage being sent to the CPU after vdroop.

 

At full idle, this is going to be less.  Assuming a 30 amp idle, and 1.6 mOhms loadline, 30 * 1.6=48mv in millivolts, so a 48mv vdroop at 30 amps, subtract that from 1520 converted to millivolts, that's 1.472v.

At the maximum 193 amp rating for 8 core parts, you get 193 * 1.6 = 308mv.  Subtract 1520-308 and you get 1.212v, which is the maximum safe vcore at 193 amps power draw.  This may seem 'low' but remember this is based up to 100C also.  And 193 amps is basically virus mode.

 

*NOTE*  These measurements are based on VCC_SENSE voltage measurements!  Some boards have VCC_Sense capability linked to a value in HWinfo64 called VR VOUT.  Asus Maximus XI boards use a recalibrated super i/o vcore sensor linked to VCC_Sense.  If your board does NOT, then the vcore reading you see may be wildly inaccurate *AND* will be more inaccurate the greater loadline calibration you use too as this affects the ground and power plane impedances even more.  Read:

 

https://www.overclock.net/forum/27686004-post2664.html

https://www.overclock.net/forum/6-intel-motherboards/1638955-z370-z390-vrm-discussion-thread-398.html#post27860326

https://www.overclock.net/forum/5-intel-cpus/1711718-9900k-overclock-results-questions-136.html#post27908122

https://www.overclock.net/forum/5-intel-cpus/1714622-9900k-large-vdroop-load-voltage-main-1-watch-2.html#post27736104

https://www.overclock.net/forum/6-intel-motherboards/1638955-z370-z390-vrm-discussion-thread-266.html#post27685780

 

 

Six core parts have a 2.1 mOhm loadline (and 4 core CFL also).  Max amps rating for 6 core CFL (4 core is lower) is 138 amps.  Doing the vdroop math (Vdroop = Amps * Resistance, or I * R) = 289.8mv.  1520 - 289=1.231v, if you are drawing 138 amps on a 8700K, 8086K, etc.  These are the maximum safe voltages on ambient cooling, up to 100C.

 

The instant you change loadline calibration away from Intel defaults of Standard/Normal (1.6 mOhms for 8 core and 2.1 mOhms for 4 and 6 core), all bets are now off, because the intel specifications are based on vdroop existing fully.  For example, if you tried setting a manual bios voltage of 1.35v and set Loadline Calibration to 0.4 mOhms (approx. equal to "Turbo" on Gigabyte and LLC6 on Asus--note the Gigabyte value was tested by me but the Asus value is a guess as I don't have an Asus board), and unless someone were willing to post load and bios voltages on *LLC7* on Maximus XI boards only (Not older boards), I cant calculate it for you), if you then tried pulling a 193 amp prime95 load or OCCT 5.0.1 Linpack load, you are going to be WAY out of specification and that CPU will degrade slowly on air cooling.

 

(1350mv - (0.4 * 193))= 1272mv=1.272v <----way out of specification here.  And transient response will be much worse as well (much larger voltage spikes and drops due to the VRM's having to work much harder and not having the full vdroop to cushion the spike and drops).

 

Also note that when you use "Auto" voltages (STILL NOT using any custom loadline calibration) rather than setting a bios voltage of 1.52v WITHOUT loadline calibration, your idle voltage will be lower, because the AC Loadline value will influence the target VID and VRM voltage that is sent to the VRM (usually around 1.4v), rather than if you used a manual override voltage of 1.52v.  This may not make much sense, but when you apply a load to the CPU (Depending on type of load and even on the AC Loadline value if it's set below the max defaults), the AC Loadline will boost the default VID and thus the VRM voltage target for you up to 1.52v (Yes, that's fully safe as long as you are NOT using a custom loadline, and are not using a positive voltage offset either).

DC loadline is responsible for dropping the VID lower but this is NOT sent to the VRM at all--it's only used for power measurements (Namely CPU Package Power, which is equal to VID * Amps).  DC Loadline's "VID droop" follows the exact same specification as VRM Loadline with respect to Vcore droop (VCC_Sense), namely VID - (Amps * DC Loadline mOhms)=VID reported to system, as opposed to VRM Vcore - (Amps * VRM Loadline mOhms)= VCC_Sense voltage.  VCC_Sense voltage is also known as true vcore or on-die sense voltage (not affected by power plane impedance, if you were measuring it with a scope, and grounded to VSS_Sense).

[JoostinOnline]

1 hour ago, Proprietary said:

Why is pumping extra voltage so dangerous anyways? If my cooler is powerful enough, can I theoretically increase the vcore infinitely?

Not at all. Your brain uses electricity too, but it's not safe to electrocute yourself as long as you stay cool.

 

Even if heat wasn't a factor, too much power will damage electrical components.

[JoostinOnline]

21 minutes ago, fluxdeity said:

It's not voltage that kills, it's amperage and temperature.

That's a very silly myth. Voltage is just as relevant as the amperage.

[Falkentyne]

8 minutes ago, JoostinOnline said:

That's a very silly myth. Voltage is just as relevant as the amperage.

This isn't so simple.

Current Intel chips are based a baseline up to 1.52v, where up to 100C, 1.52v to VCC_Sense must have a 0 amp load going to the CPU, and must be subject to Intel default loadline slope.  Yes, higher than 1.52v is NOT safe (even at idle) unless you go sub ambient.  This loadline is 1.6 mOhms for 8 core CFL and 2.1 mOhms for 4 and 6 core.  Using loadline calibration throws a huge wrench into this.  I explained in more detail above.