AMD CPU tweaking

[Islam Ghunym]

I am trying to make most out of an AMD Zen2 3700X chip at low power demands (Ex: 30 watts) + OCed memory to limits (frequency + all timings and sub-timings) so I have some questions that I want to discuss:

There are different settings that may achieve that if combined and used properly. I just can't determine what should I do:

1- CPU core Voltage: the lower it is, the less power it will demand + less clocks will be achived

2- PPT or Soc Power in watts: the lower it is, the less power of course

3- EDC: the higher it is the more power it will consume

4- DRAM Voltage: should be 1.45 with OCed memory.

5- LLC: it controlls the way voltages scale with Amps

6-VRM frequency:

There maybe even more that I am not aware of.

 

My thoughts are:

if I limited Amps and placed high voltages +offsets while LLC on medium I will probably achieve higher clocks at  the limit 30 watts for example, but that will increase the idle power consumption.

If I increased LLC to extreme and placed an -offset voltage on cores then placed a limit on Soc power "PPT" I will probably idle at lower power, but not sure if i i will reach less stable clocks on load

Not sure if VRM frequency would help

 

Not sure if anything I wrote even right!

[Jurrunio]

12 minutes ago, Islam Ghunym said:

if I limited Amps and placed high voltages +offsets while LLC on medium I will probably achieve higher clocks at  the limit 30 watts for example, but that will increase the idle power consumption.

No you'll just hit the current limit early

 

13 minutes ago, Islam Ghunym said:

If I increased LLC to extreme and placed an -offset voltage on cores then placed a limit on Soc power "PPT" I will probably idle at lower power, but not sure if i i will reach less stable clocks on load

Extreme LLC = extreme voltage spikes, not good for hardware nor power draw

 

basically what you thought about doing are all wrong. If you want most performance out from small power budget (why?), just set the power limit (PPT) to 30w , use medium LLC and as low voltage offset as possible. You can test with different values of TDC and EDC, while the rest of the CPU variables should stay at stock numbers.

[Islam Ghunym]

3 minutes ago, Jurrunio said:

Extreme LLC = extreme voltage spikes, not good for hardware nor power draw

 

basically what you thought about doing are all wrong. If you want most performance out from small power budget (why?), just set the power limit (PPT) to 30w , use medium LLC and as low voltage offset as possible. You can test with different values of TDC and EDC, while the rest of the CPU variables should stay at stock numbers.

Exterme LLC will be harmfull only if I set high voltages, however the voltage spike won't inctease power consumption for small fraction of second, right?

[jj9987]

23 minutes ago, Islam Ghunym said:

if I limited Amps and placed high voltages +offsets while LLC on medium I will probably achieve higher clocks at  the limit 30 watts for example, but that will increase the idle power consumption.

Wattage = Voltage * Current

 

If you keep wattage the same and increase the voltage, this results in much less amps. If CPU can't have the amps it needs at a given voltage, it might result in instability or simply not clocking as high, so not getting those higher clocks.

[Jurrunio]

1 minute ago, Islam Ghunym said:

Exterme LLC will be harmfull only if I set high voltages, however the voltage spike won't inctease power consumption for small fraction of second, right?

you will be running higher voltages since voltage dips also get more significant with extreme LLC, these voltage dips means you need higher average voltage in order to not crash

[Islam Ghunym]

1 minute ago, Jurrunio said:

you will be running higher voltages since voltage dips also get more significant with extreme LLC, these voltage dips means you need higher average voltage in order to not crash

That why I said I wanted to combine that with -offset voltage so..?

[Islam Ghunym]

10 minutes ago, Jurrunio said:

you will be running higher voltages since voltage dips also get more significant with extreme LLC, these voltage dips means you need higher average voltage in order to not crash

So I will crash in the end  if I did -offset, but would that be helpfull if combined with power limit which would limit amps.

What I want exterme LLC to do is to prevent vdroops while keep limiting power

[Jurrunio]

12 minutes ago, Islam Ghunym said:

That why I said I wanted to combine that with -offset voltage so..?

You dont understand what LLC does to the voltage controller. Extreme LLC makes it go haywire at an attempt to not drop voltage under load. However it only reacts to voltage drop, it cannot forsee when the CPU will change current draw which affects the voltage, causing the scary voltage spikes and dips. The CPU will crash when it gets too little voltage in the dips, even if it lasts a really short period of time In order to compensate you'll need to run higher voltage so the dips clear the CPU's minimal voltage, which is bad for your power draw.

 

10 minutes ago, Islam Ghunym said:

So I will crash in the end  if I did -offset, but would that be helpfull if combined with power limit which would limit amps.

What I want exterme LLC to do is to prevent vdroops while keep limiting power

Extreme LLC does more than what you see, it's not as good as it seems on paper.

[Islam Ghunym]

2 minutes ago, Jurrunio said:

You dont understand what LLC does to the voltage controller. Extreme LLC makes it go haywire at an attempt to not drop voltage under load. However it only reacts to voltage drop, it cannot forsee when the CPU will change current draw which affects the voltage, causing the scary voltage spikes and dips. The CPU will crash when it gets too little voltage in the dips, even if it lasts a really short period of time In order to compensate you'll need to run higher voltage so the dips clear the CPU's minimal voltage, which is bad for your power draw.

Hold on a second. what I already know is:

At a certain voltage when CPU goes to load, it will cause a Vdroop then it will stabilize again because amps changed.

What will LLC do is removing this drops when set at higher than medium ending up increasing voltages more than what are already set by bios settings.

So if I set for example a certain voltage Ex: 1.2. When CPU goes under load, Extreme LLC will increase the outpot voltage to 1.3 or even more and those can be serious if the reference voltage is high

[Jurrunio]

5 minutes ago, Islam Ghunym said:

set at higher than medium ending up increasing voltages more than what are already set by bios settings.

that's not always the case. Usually it happens with the second or third highest settings

 

5 minutes ago, Islam Ghunym said:

So if I set for example a certain voltage Ex: 1.2. When CPU goes under load, Extreme LLC will increase the outpot voltage to 1.3 or even more and those can be serious if the reference voltage is high

Voltage is in wave form, never a flat line. CPU's current draw is really unstable and VRM runs in phases, so it's never capable of staying completely flat

[Islam Ghunym]

15 minutes ago, Jurrunio said:

that's not always the case. Usually it happens with the second or third highest settings

 

Voltage generated is in wave form, never a flat line.

Well I know, but I still didn't get what you meant.

I mean why extreme LLC won't help if it hides the vdroops. Why it would take more power if current is already limited and why it would be dangerous if -offset is already set and why it will make use off more power if voltages spikes does not happen in realtime? I am just lost here. It looks like things won't be explained with just words. Can you forward me pls somewhere that can clarify for me?

Edited March 8, 2020 by Islam Ghunym

[Jurrunio]

14 minutes ago, Islam Ghunym said:

I mean why extreme LLC won't help if it hides the vdroops

I'm talking about instantaneous voltage (i.e. what an oscilloscope sees) while your mind is still stuck on average voltage (what software reports and DMM sees), we arent going anywhere until you get past this

[Islam Ghunym]

27 minutes ago, Jurrunio said:

I'm talking about instantaneous voltage (i.e. what an oscilloscope sees) while your mind is still stuck on average voltage (what software reports and DMM sees), we arent going anywhere until you get past this

Nope I already know that.

when we talk about power consumption then average voltage only matters here and I think you know that. Power draw is not related to your instantaneous voltages which I am trying to tweak to achieve higher clocks. So if you are not aware don't attack my understanding. Look at yours.

For a moment I thought I would learn something. Thank you, you already said much.

Your statements stayed out of logic even after asking several times.

[Jurrunio]

8 hours ago, Islam Ghunym said:

Nope I already know that.

when we talk about power consumption then average voltage only matters here and I think you know that. Power draw is not related to your instantaneous voltages which I am trying to tweak to achieve higher clocks. So if you are not aware don't attack my understanding. Look at yours.

For a moment I thought I would learn something. Thank you, you already said much.

Your statements stayed out of logic even after asking several times.

An example will work better if concepts dont work for you

 

Let's say your CPU needs a minimum of 0.8V to be stable at 2.4GHz, and a VRM which when set to no LLC with C-states disabled (which only affects idle voltage anyway) will give you say, 0.95V idle, 0.85V average and 0.8V minimum. At extreme LLC and the same voltage target (i.e. what you entered in the BIOS), now it will do 0.98V idle, 1.05V average and 0.95V minimum. You can lower that down by 150mV so it hits the same 0.8V minimum while idle will be 0.83V, but the average is still at 0.95V. You're drawing more power for essentially, the same clock speed.

[Islam Ghunym]

12 hours ago, Jurrunio said:

An example will work better if concepts dont work for you

 

Let's say your CPU needs a minimum of 0.8V to be stable at 2.4GHz, and a VRM which when set to no LLC with C-states disabled (which only affects idle voltage anyway) will give you say, 0.95V idle, 0.85V average and 0.8V minimum. At extreme LLC and the same voltage target (i.e. what you entered in the BIOS), now it will do 0.98V idle, 1.05V average and 0.95V minimum. You can lower that down by 150mV so it hits the same 0.8V minimum while idle will be 0.83V, but the average is still at 0.95V. You're drawing more power for essentially, the same clock speed.

Ok, not sure from where you got these numbers to prove that average will be higher as there is no explanation why these numbers would appear, but That will be different on every motherboard depending on how manufacturer has designed how to compensate for spikes as more LLC level will also stress VRM components and lower the efficiency in general.

 

I found that: LLC is found to make overclockers able to reach higher voltages on load because they can't put higher idle voltage (Ex: 1.43V on intel while idling and maybe 1.35V on load so they can't increase load voltages by going out of safe voltage range on idle)

so with higher levels of LLC the Vdroop will decrease and we will get higher load voltage as we will get a spike for a short duration while going back to idle  "a matter of ms" which should not be a problem usually if it is not very high like 2 volts.

 

There is no point of using LLC that will decrease VRM efficiency while you can put a higher idle voltage like while undervolting.

When undervolting LLC should be at lowest level as we don't care about core VID here. I mean Fuck it! Let it drop since I am already droping voltages myself! It does not make any sense! why I should prevent that droop. I feel like a big idiot.

 

So I should go for lowest LLC level possible and undervolt as required.

 

Another thing is that because voltage decides how much current is going into the CPU, I simply should not care about that too. That matters only when overclocking as those will limit the CPU current at high voltages preventing hugher clocks.

 

Also limiting total power won't change anything as it will limit the current and why I should limit current while I can limit voltage. I should simply let the CPU take what it needs and only tweak voltages. There is no magical thing to be done. I just made things more complicated while they are simple.