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Why you should undervolt your Ryzen 3000 - Part II

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post #1 of 134 (permalink) Old 01-04-2020, 08:33 AM - Thread Starter
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Why you should undervolt your Ryzen 3000 - Part II

Hear me out! I know we had this theory before!
Thanks to The Silt writeup on FIT and VFT curves, i finally understand AMD have made Ryzen 3000 closer to GPU boosting than old Intel Turbos.

The biggest problem with initial testings, the reviewers did not fully unclock the PBO motherboard limits!
Which being the PPT, TDC and EDC limits of your motherboard to supply unlimited powah to Ryzen 3000.

Back to the VFT curve, volt, freq and thermals.

Zen2 follows a strict VF curve, depending on chiplets, every cores can only run at x'Ghz with y'Volts, at certain temp. Go past that thermal mark, it will drop a multiplier or more.
As such you see core temps are the ultimate decisions at how long you can boost to. Sure say a 3950X can boost to 4.7Ghz at 1.45v, but without strong cooling, it wil not sustain for long.

So to keep thermals down, you can use super chiller cooling or you live in sub 20c ambient or you simply undervolt it! Hear me out again!
Now consider how small the 3000 IHS is, how small 7nm is, to dissipate heat with a regular WC is tougher than ever0! Again thanks to Silt, who calculated the heat density, regular WC and regular ambient are not conducive enough to remove heat fast! The key word is fast!

So now with undervolt, your VF curve shift downwards, so you go from 1.45v to 1.4v, and your boost clocks drops to 4.65Ghz. However, your temps are down 5-8C, which means 4.65Ghz is able to sustain longer!

Back to the bolded, now try with PBO on, +200Mhz, and unlock your PPT/TDC/EDC values, return all LLC to default vdroop. Disable PBO Scalar too.
The goal is to lower voltages as much as we can, while supplying as much current and power the CPU can accept.
Don't worry the FIT inside the chiplets will maintain stability of lowered voltages and the safety levels of current it can absorb!

On assumption you already have a good cooling solution, say a Noctua or 240mm AIO
Be prepared to be surprised!

Sooo
Set vcore to 'normal', and offset -0.05v for start.
vcore LLC to 'normal'
soc LLC to 'high', if you are overclocking ram, else normal
Set the edc in CBS/XFR to 155. tdc to 125. ppt to 185. scalar to 1x.
In Amd overclocking menu, there is PBO handoff to 'motherboard' and autoOc settings to +200


Last edited by dansi; 02-15-2020 at 09:14 PM.
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post #2 of 134 (permalink) Old 01-04-2020, 08:39 AM - Thread Starter
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The above applies only to auto boost mode, to squeeze as much out of AMD FIT behavour. If you are already manually overclocking, you can ignore everything! Manually overclocking should grant you superior all core results as long your chiplets can do >4.2Ghz, however you do lose out on low cores results.

Manual overclock disable FIT and VFT curves, so you are on your own without protection. There may have been cases of degregation or not due to this

Last edited by dansi; 01-04-2020 at 11:32 AM.
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post #3 of 134 (permalink) Old 01-04-2020, 10:16 AM
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Quote: Originally Posted by dansi View Post
Hear me out! I know we had this theory before!
Thanks to The Silt writeup on FIT and VFT curves, i finally understand AMD have made Ryzen 3000 closer to GPU boosting than old Intel Turbos.

The biggest problem with initial testings, the reviewers did not fully unclock the PBO motherboard limits!
Which being the PPT, TDC and EDC limits of your motherboard to supply unlimited powah to Ryzen 3000.

Back to the VFT curve, volt, freq and thermals.

Zen2 follows a strict VF curve, depending on chiplets, every cores can only run at x'Ghz with y'Volts, at certain temp. Go past that thermal mark, it will drop a multiplier or more.
As such you see core temps are the ultimate decisions at how long you can boost to. Sure say a 3950X can boost to 4.7Ghz at 1.45v, but without strong cooling, it wil not sustain for long.

So to keep thermals down, you can use super chiller cooling or you live in sub 20c ambient or you simply undervolt it! Hear me out again!
Now consider how small the 3000 IHS is, how small 7nm is, to dissipate heat with a regular WC is tougher than ever0! Again thanks to Silt, who calculated the heat density, regular WC and regular ambient are not conducive enough to remove heat fast! The key word is fast!

So now with undervolt, your VF curve shift downwards, so you go from 1.45v to 1.4v, and your boost clocks drops to 4.65Ghz. However, your temps are down 5-8C, which means 4.65Ghz is able to sustain longer!

Back to the bolded, now try with PBO on, +200Mhz, and unlock your PPT/TDC/EDC values, return all LLC to default vdroop. The goal is to lower voltages as much as we can, while supplying as much current and power the CPU can accept. Don't worry the FIT inside the chiplets will maintain the safety levels of current it can absorb!
On assumption you already have a good cooling solution, say a Noctua or 240mm AIO

Be prepared to be surprised!
Let's put this into perspective, look I am a manual overclocker as I get a lot more from manual overclocking then using stock or PBO. But I though as proof I'll drop some screen shots here. First I ran stock, no PBO with AUTO vcore, second screenshot is stock no PBO with -0.05 vcore offset. The third screenshot it PBO with AUTO vcore and the last screenshot is PBO with -0.1 vcore offset. I did -0.1 offset with PBO as I found -0.05 did not yield much, but -0.1vcore offset at stock resulted in dropped results. I also added Hwinfo64 in the sceenshots to see max load temps.
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post #4 of 134 (permalink) Old 01-04-2020, 11:05 AM - Thread Starter
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Thanks bud! 5% uplift just by undervolting with PBO!
Did you also max out the 3 PBO limits or at least increase them a bit more than the original values?

Quoting GN

Code:
Package Power Tracking (“PPT”): The PPT threshold is the allowed socket power consumption permitted across the voltage rails supplying the socket. Applications with high thread counts, and/or “heavy” threads, can encounter PPT limits that can be alleviated with a raised PPT limit.
Default for Socket AM4 is at least 142W on motherboards rated for 105W TDP processors.
Default for Socket AM4 is at least 88W on motherboards rated for 65W TDP processors.

Thermal Design Current (“TDC”): The maximum current (amps) that can be delivered by a specific motherboard’s voltage regulator configuration in thermally-constrained scenarios.
Default for socket AM4 is at least 95A on motherboards rated for 105W TDP processors.
Default for socket AM4 is at least 60A on motherboards rated for 65W TDP processors.

Electrical Design Current (“EDC”): The maximum current (amps) that can be delivered by a specific motherboard’s voltage regulator configuration in a peak (“spike”) condition for a short period of time.
Default for socket AM4 is 140A on motherboards rated for 105W TDP processors.
Default for socket AM4 is 90A on motherboards rated for 65W TDP processors.
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post #5 of 134 (permalink) Old 01-04-2020, 11:19 AM - Thread Starter
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Other things to consider, on some motherboards, Auto may add vcore or LLC.
What you want, is to supply the same vcore as vid request, before the undervolt settings, and with stock vdroop as needed by FIT. Make sure your boards dont add voltages itself. Yes, even turn off LLC for the soc .

Secondly, you dont want to undervolt too much, that your single/low cores get affected. You want to at most lose 0.25Ghz from the lowered vcore. This is trial and error, but -0.1v is a good start.
Once you find a good balance between all cores and low cores undervolt, you will be surprised your low cores can perform as good if not better than with no undervolt!
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post #6 of 134 (permalink) Old 01-04-2020, 12:12 PM
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For my setup, PBO disabled and -0.100V offset results in about 2-300 better score in CB20
PBO enabled in any form, will result in lower scores and higher temperatures.
Attached Thumbnails
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Name:	PBO disabled -0.1000V.png
Views:	645
Size:	1.71 MB
ID:	316426  


R9 3950X
(26 items)
CPU
Ryzen 3950X
Motherboard
Gigabyte X570 Aorus Xtreme
GPU
ASUS GeForce GTX 1080 Ti ROG STRIX GAMING O11G 11GB DDR5X 352-bit
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F4-3600C18Q-64GTZN
Hard Drive
GIGABYTE AORUS 1TB PCI Express 4.0 x4 M.2 2280
Hard Drive
Seagate IronWolf 8TB SATA-III 7200RPM 256MB
Hard Drive
Seagate IronWolf 8TB SATA-III 7200RPM 256MB
Hard Drive
Seagate IronWolf 8TB SATA-III 7200RPM 256MB
Power Supply
Seasonic PRIME Ultra , 80+ Titanium, 750 W
Power Supply
APC Smart-UPS 2200VA
Cooling
Fractal Design Celsius S36 Black
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Alphacool 14 W/mk thermal pad
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Operating System
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Microlab SOLO 6C NEW
Other
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Other
Noctua NF-A14 PWM
Other
Noctua NF-A14 PWM
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post #7 of 134 (permalink) Old 01-04-2020, 12:21 PM
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Quote: Originally Posted by Deepcuts View Post
For my setup, PBO disabled and -0.100V offset results in about 2-300 better score in CB20
PBO enabled in any form, will result in lower scores and higher temperatures.
Dude, I know why... i totally found your issue. YOU HAVE A FORD EMBLEM near your name... Take that **** off and your scores will fly

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post #8 of 134 (permalink) Old 01-04-2020, 01:16 PM
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Bad advice as far as gaming FPS.

Tested 3950x,3800x,3600x & 3500x.

-.50 cpu offset.Clocks drop 0-300MHz on average.Temps drop 0-3C.No joy for FPS.

Moral of story.Keep your cpu as cool as possible.Let it do its thing.
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post #9 of 134 (permalink) Old 01-04-2020, 06:42 PM
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Quote: Originally Posted by dansi View Post
Thanks bud! 5% uplift just by undervolting with PBO!
Did you also max out the 3 PBO limits or at least increase them a bit more than the original values?

Quoting GN

Code:
Package Power Tracking (“PPT”): The PPT threshold is the allowed socket power consumption permitted across the voltage rails supplying the socket. Applications with high thread counts, and/or “heavy” threads, can encounter PPT limits that can be alleviated with a raised PPT limit.
Default for Socket AM4 is at least 142W on motherboards rated for 105W TDP processors.
Default for Socket AM4 is at least 88W on motherboards rated for 65W TDP processors.

Thermal Design Current (“TDC”): The maximum current (amps) that can be delivered by a specific motherboard’s voltage regulator configuration in thermally-constrained scenarios.
Default for socket AM4 is at least 95A on motherboards rated for 105W TDP processors.
Default for socket AM4 is at least 60A on motherboards rated for 65W TDP processors.

Electrical Design Current (“EDC”): The maximum current (amps) that can be delivered by a specific motherboard’s voltage regulator configuration in a peak (“spike”) condition for a short period of time.
Default for socket AM4 is 140A on motherboards rated for 105W TDP processors.
Default for socket AM4 is 90A on motherboards rated for 65W TDP processors.
Yup I did increase them for both test with and without OFFSET

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post #10 of 134 (permalink) Old 01-04-2020, 07:45 PM - Thread Starter
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Quote: Originally Posted by Forsaken1 View Post
Bad advice as far as gaming FPS.

Tested 3950x,3800x,3600x & 3500x.

-.50 cpu offset.Clocks drop 0-300MHz on average.Temps drop 0-3C.No joy for FPS.

Moral of story.Keep your cpu as cool as possible.Let it do its thing.
Can we know more of your setup? Boards, bios version, chipset drivers, bios settings.
In general, get the latest software firmware everything. I won't discount AMD have also fixed their PBO to run correctly, hence the earlier testings may be outdated.

In bios, did you use +200, turn off LLC, turn up the 3 PBO values?
-0.5 is too high, try -0.1 first. losing 300mhz is too much, you want to keep it within 50mhz, which is completely doable.
It is a balancing act, just need to hit that right amount of offset and you get better multicore and single core sustained performance.

Yes granted, i have noticed in certain games benchmark, the clocks were lower, just a tick, but the performance remains the same.

But also yes, keeping Ryzen 3000 cool is the key. Just that, doing it fast enough is a challenge. You can have multiple rads, it will help but your water block is still not fast enough to control the VFT curve to achieve higher sustain clocks. Voltage seems to be the answer for now until 7nm. 7nm+ bins improved with lower vid requirements

Last edited by dansi; 01-09-2020 at 10:01 PM.
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