04-25-2020 11:11 AM - last edited on 03-05-2024 07:05 PM by ROGBot
04-25-2020 11:42 AM
04-25-2020 12:25 PM
04-25-2020 01:06 PM
Falkentyne wrote:
On fixed voltage, what you want, measured with an *OSCILLOSCOPE*, is the LOWEST PEAK TO PEAK voltage, with the lowest AVERAGE load voltage. That's your goal.
Arne Saknussemm wrote:
You need an oscilloscope to study this stuff accurately...it's all about transient response.
LLC 5 or 6 is a good place to be for a happy OC...get away with lower LLC if you can....Vdroop is a good thing if you want your CPU to live long and prosper....
04-25-2020 01:16 PM
joppiano wrote:
Thanks for the reply.
So, if it's the "lowest peak-to-peak at the lowest average load voltage" that is the goal, and that can only really be monitored with an oscilloscope - is there any rule of thumb that can be used when only monitored in windows?
Also as said, my previous understanding of LLC was to get as close to a flat transition as possible - but that turned out not to be true, since you would just pick the LLC setting with 0 vdroop, and as stated - you WANT vdroop to take care of the transient respond that is occuring when going from load to idle, idle to load.
Personally, if I go with LLC 5, I will get some decent vdroop. If I go with LLC 6, I will according to windows get a vboost, but as confirmed above, I do get a vdroop, it is just not showing in windows. But my avg voltage is lower - but I have NO IDEA if my transient are better or not.
As shown in the spreadsheet, I can get along with lower average voltage with LLC 6 than with LLC 5, which is good - But if transient dips & spikes are worse, that is worse, due to peak-to-peak is bigger all of the sudden. Or at least can be.
So, about the calculation mOhms of each LLC level on ASUS, how do I calculate how many amps I am pushing. I know you divide watts with voltage. But is it voltages under load you use, or voltages at idle (set in bios) ?
(Watts / voltage under load or Watts / voltage set in bios)
Because if I can figure out that calculation, I can calculate the mOhms of resistence on each individual LLC level on ASUS Z390.
Also, how did you determine the transient dips & spikes in your 3 examples?
So when you say "lower LLC" I assume you mean LLC 4 or maybe even LLC 3 - so MORE vdroop and not less, yes?
04-25-2020 01:46 PM
Falkentyne wrote:
Less LLC=more vdroop. But too much vdroop is bad on fixed vcore because you need a too high idle voltage to compensate.
Rule of thumb is, medium levels of LLC (not too low, not too high) are good on fixed vcore.
04-25-2020 03:40 PM
joppiano wrote:
Okay that explains alot then.
That is why LLC 6 is seemingly stable on lower voltages, than it will be on LLC 5. (Obviously more thorough & longer testing is needed)
On LLC 5 I will archieve more vdroop - but I need a higher average voltage to compensate for that.
On LLC 6 I will archieve less vdroop - but I can use a lower average voltage.
But LLC 6 isn't "medium" hmm.
However, looking at elmors website ( https://elmorlabs.com/index.php/2019-09-05/vrm-load-line-visualized/ ) I would assume that LLC 4, 5 & 6 would be the best, if you just look at the graph of the transient.
But according to your previous statement, it seems that LLC 3 is the best option in that specific test case. That has the lowest peak-to-peak, but also a lot of vdroop. It actually seems that LLC 1 to LLC 3 is the best in that test case.
But if LLC 5 is around 1.05 mOhms on Asus z390, that seems like A LOT of vdroop that is not visable in windows what so ever.
Using elmors spreadsheet https://docs.google.com/spreadsheets/d/1nKdrj_eoxxXdsAkL6lj-EOdHj06khw1tN0fxVOR3mlc/edit#gid=0 and putting in 1.310v, it should droop to 1.210v at 100amps. That seem extremely low ?
On my board (Z390-F), LLC goes from 1-7. So assuming LLC 7 is 0 mOhms, LLC 6 is probably around the 0.4 mOhms area.
04-25-2020 04:29 PM
Falkentyne wrote:
It varies motherboard to motherboard. And each motherboard has different transient response. The evga z390 dark for example is literally in a league on its own. But a board with that good transient response without any die-sense vcore readings...I guess they designed this board for world records...
04-25-2020 07:05 PM
joppiano wrote:
I see.
But looking at elmors website https://elmorlabs.com/index.php/2019-09-05/vrm-load-line-visualized/ - would you agree that LLC 3 is the best option, since that has the lowest peak-to-peak voltages ?
In his case, even LLC 1 & 2 outperforms LLC 4 & 5, since peak-to-peak voltages are lower.
But LLC 1 & 2 would require a higher average voltage than LLC 4 & 5, to remain stable at same workload right?
- UPDATE:
When talking about stability.
Can instability take place, if low peaks or high peaks is to low/high ? Or is it mainly the voltages under load that causes it.
If we assume LLC 5 is around 1.05 mOhms and we assume LLC 6 is around 0.4 mOhms.
Example 1: (1.365v BIOS & LLC 5)
180W / 1.365v = 132 amps.
132 amps * 1.05 mOhms = 139mv Vdroop.
0.139v - 1.365v = 1.226 @ load.
Example 2: (1.315v BIOS & LLC 6)
180W / 1.315v = 137 amps.
137 amps * 0.4 mOhms = 55mv Vdroop.
0.055v - 1.315v = 1.260v @ load.
Example 1 & Example 2 is running the same load with P95, but how come Example 1 is passing 2 hours of P95, but Example 2 is failing after 30 minutes with BSOD & Worker Stopping ?
Example 2 has a higher vcore @ load - so is this instability caused by bad transient response ?
04-25-2020 08:08 PM
Falkentyne wrote:
Oh, I forgot about that. However Elmor's chart isn't based on a heavy load. He took those graphs while idle in the BIOS.
At a very heavy load, the spikes and dips on both ends will be larger than anything shown on these graphs, but how much larger will depend on the VRM quality and the inductors and capacitors.
Here is a 100 amp load, prime95, done with a 1.50v bios set point, LLC1 and LLC8. You can see my LLC8 math way above is pretty accurate at least 😕
https://www.overclock.net/forum/6-intel-motherboards/1638955-z370-z390-vrm-discussion-thread-413.htm...
Pretty sure 193 amps will be quite worse.
Maybe Shamino can jump in on this? He's probably extremely busy though 😞
My math was just me guessing from my head randomly. I forgot that with a large loadline slope, your idle voltage will have substantial vdroop on that.
I forgot that with LLC1 or LLC2, the voltage you set in BIOS won't spike above that point (e.g. 1.20v will be 1.17v or 1.18v).
So technically yes you are correct. But the problem again is the high idle voltage. You don't want your computer to be sitting constantly at 1.48v because you set 1.520v in BIOS with LLC2 to do a 193 amp prime95 run (drops to 1.213v). It's better to do 1.38v + LLC5 in that case. Or consider offset or adaptive modes.