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post #1 of 8 (permalink) Old 02-07-2020, 10:21 AM - Thread Starter
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Vcore Question

Probably dumb but this 1.35v limit.... Is that at full load prime 95 small tft holy god avx type load, or is it 1.35v absolute max ever?

I have a 7350k running 4.9ghz 0 avx offset, 4.5 uncore. Vcore in bios is set to 1.38v.. Llc is level 3. At idle I'm at 1.38 but under p95 small/avx (latest version p95) it drops to 1.344v.. So am I good or what? I've Googled this a ton and not really seen anything that answers it. I mean saying 1.35 limit but never saying loaded actual vcore multimetered limit kinda leaves a lot of questions.

One thing showed idle is meaningless because there are no amps so voltage being high is not a problem, but I'd like more of an input on all this since I have yet to find anything that directly answers actual measured vcore limits at idle and loaded.

This is on an asrock z270 taichi btw..

Thanks guys
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post #2 of 8 (permalink) Old 02-07-2020, 10:42 AM
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Are you saying that it is recommended to stay at 1.35v or lower? I'd say stay at 1.4 or lower personally. If your chip is really cool maybe 1.45.

It's impossible to know when/if your chip is gonna degrade. If you plan on using it for a long time I would stay below 1.4v.

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post #3 of 8 (permalink) Old 02-07-2020, 03:43 PM - Thread Starter
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1.35 or 1.4 whatever the case that wasn't my concern. I'm saying where and when is that measured? Is it the number I type into the bios, is it the voltage when its at idle, is it the voltage when its under the highest load I can put it under (p95 small tft), or what? Because I see everyone saying their voltage but that number could be all over the place. To me the 1.35 or 1.4, whatever you prefer, is the vcore measured with a multimeter, at the highest load you can put the cpu under. Is this true? Is it also true that idle voltage can be high and not matter? Or is everyone preaching idle vcore or simply the number they are typing into the bios with disregard to actual voltage altogether..
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post #4 of 8 (permalink) Old 02-07-2020, 06:52 PM - Thread Starter
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Here's what I mean, now that I'm home and can test it. I used 2 multimeters just so I knew there was no error. Then compared it to HWiNFO. Here's what I got. Now you see what I mean. To me if the magic limit is 1.35 or 1.4, it should be the cap using a meter and under a load. Obviously HWiNFO isn't showing us the truth at all. Which would further question people's vcores they brag about, when they could be at an entirely different voltage. Most are at level 1 and look how far off it is.. Is this normal? Is everyone actually at way different voltages than they think they are? I'm beginning to wonder.
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post #5 of 8 (permalink) Old 02-07-2020, 07:20 PM
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Quote: Originally Posted by Nikado7 View Post
Here's what I mean, now that I'm home and can test it. I used 2 multimeters just so I knew there was no error. Then compared it to HWiNFO. Here's what I got. Now you see what I mean. To me if the magic limit is 1.35 or 1.4, it should be the cap using a meter and under a load. Obviously HWiNFO isn't showing us the truth at all. Which would further question people's vcores they brag about, when they could be at an entirely different voltage. Most are at level 1 and look how far off it is.. Is this normal? Is everyone actually at way different voltages than they think they are? I'm beginning to wonder.
You measured with a meter from the onboard read points, right? Or did you measure from behind the socket?

In order to get an accurate reading, you need to measure directly from the VRM.
If you do not, your measurement will show a voltage rise due to 'voltage drop' across the power plane, also known as power plane impedance. This "voltage drop" causes what you MEASURE to be higher than what is really there.

It's basically the same thing as this: (notice the voltage read points are affected):

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

In order to avoid this, you need to measure as close to the VRM as possible. You want the "on-die sense" reading.
Even if you measure from the caps behind the CPU socket, you're going to run into the impedance issue.

tl;dr: HWinfo64 is accurate on the Maximus XI boards.

I quote from Elmor:

Quote:
When measuring voltages on a motherboard and large currents are involved, it's important to use accurate measurement points due to resistance/impedance present on the board. The power plane for example can be modeled as a resistor connected in series between the VRM output and the target device, together with Ohm's law, U = R*I. The larger the current, the larger the voltage drop. If you measure the voltage at the VRM output, for example at the inductor, you'll see a large difference compared to the voltage measured at the CPU socket MLCC. What we're interested in is what voltage the CPU die is actually getting after passing through the output filter, power plane, socket and package.
Quote:
Something to look out for is when you're seeing a voltage reported during load which is much higher than what you've set. It would require a negative load-line which is just not supported on any controller as far as I know. At 0 mOhm load-line, you get exactly what you set (Level 8 on M11).

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post #6 of 8 (permalink) Old 02-07-2020, 07:54 PM - Thread Starter
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Hmmmm, lots of help but that brings me to the next question, how do I measure on die sense? VRM is a collective term for several components so it doesn't really narrow it down. I don't have those fancy labeled measurement points on this motherboard, unless you're saying those aren't accurate either so it wouldn't matter? Just trying to figure this out once and for all. Hwinfo jumps from 1.296 to 1.312 with no in between, then 1.344, it has these intervals and it jumps from one to the other and that doesn't make any sense to me at all when the load is constant. My meter doesn't show that crap, so that's why I'm here and am doubting hwinfo.

I was measuring the caps yes.
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post #7 of 8 (permalink) Old 02-07-2020, 08:33 PM
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Quote: Originally Posted by Nikado7 View Post
Hmmmm, lots of help but that brings me to the next question, how do I measure on die sense? VRM is a collective term for several components so it doesn't really narrow it down. I don't have those fancy labeled measurement points on this motherboard, unless you're saying those aren't accurate either so it wouldn't matter? Just trying to figure this out once and for all. Hwinfo jumps from 1.296 to 1.312 with no in between, then 1.344, it has these intervals and it jumps from one to the other and that doesn't make any sense to me at all when the load is constant. My meter doesn't show that crap, so that's why I'm here and am doubting hwinfo.

I was measuring the caps yes.
You need to measure from a cap right next to the VRM controller.
Good luck without a schematic. You could easily fry something if you probe the wrong thing.
You could alternatively solder a wire directly to the VCC_Sense (live) and VSS_Sense (ground) pins directly on the CPU.

You can see an example at 7:30 in this video here.


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post #8 of 8 (permalink) Old 02-08-2020, 05:20 AM - Thread Starter
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In that video he said if you use the next section on HWiNFO, the IR35201 VR OUT, that it is very accurate. Even he said the vcore measurement on there is measuring who knows what. He even said vcore was using 12mv increments because of who knows what, same as I was seeing. So, I used the VR OUT and redid my tests. Now everything actually makes sense.
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