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[JohnnyFootball]

I have experience undervolting through PBO. I was running my 7700X with a -30 offset, a max temp of 85C and a max power of 85W and while I lost a little performance temps dropped from 90C to around 61C in Cinebench.


I upgrade to a 7800X3D and it would seem at first to be stable with a -30 offset as well as 85C and 85W powerdraw, but I started getting some game crashes and I ran Cinebench and dropped the offset to -20. It seems fine.
However, the temps are constantly coming close to the 85C. That's fine, as the CPU is (supposedly) designed to handle those temps, but I still feel I can drop them.

Not quite and here is where I am hoping someone with real experience can help.

Well I have been reading that in order to get the most out of your system. You need to really have each core do it's own offset with the highest performing cores having the least undervolt. I have also read the Cinebench is not the best indicator of stability as undervolting stability issues more come into play at idle loads.

My question to anyone with experience, how do you go about finding the best performing cores and how do you go about testing individual configurations. I get that it's not likely a quick process, but I am inspired to play around with it to have the quietest fastest system possible.

My main focus is keeping the temps as low as possible with minimal loss in performance.

Thanks!

 

[PaintTinJr]

I think your chances of finding people that have done this are going to be slim, so sadly can't say I've actually done it but if some suggesting a methodology is helpful, then here's what I would suggest.

Your test software would need to be memtest86., which I suspect you are already familiar with having previously undervolted and got a stable machine. If not, it is the defacto means of testing stable overclocking and is a minimal linux boot disk that does all sorts of memory testing that stresses the CPU and memory for stability. IIRC once you've decided on a final config it is supposed to run for at least 24hrs straight without any errors, and probably tested in summer and winter ambient conditions.

As for finding the fast cores, it is probably different with AMD and Intel because of the chiplet design, so you'd probably need to test Core Pairs, and I would assume AMD design allows the primary core/chiplet to be selected, in the bios with all others disabled, whereas in the past, I'm pretty sure Intel's primary core is fixed, and you can only turn off the other cores, but as your hardware is a AMD 7800X3D, that's neither here nor there.

As a methodology, I would think testing each chiplet(Core pairs) - with all others disabled - and clocking the memory as low as allowed and the CPU clock as high as you can to see which chiplets handle the best clock and thermals while under-volting - maybe doing a full 20min PSU disconnected at wall socket in between tests to remove residual CPU heat after 1hr tests - would let you order them from best to worst. In theory the chiplet handling the best clock and thermals at the lowest power is superior to the others. how those chiplets perform when memory is working at higher clocks and all chiplets are stressing the infinity fabric(northbridge?) may impact thermals that change the order, but it should be a reasonable starting point for the info you are wanting to test IMO.

As a general point, i would suggest you running memory at below spec to free up stability and thermal headroom, and using as few modules as possible to make pairing/matching easier, because memory stability works against overclocking/undervolting going by the video I watched of Linus. In his video the manufacturer supplied and custom matched highest spec memory modules, and he had been told by the manufacturer to downclock the memory from the top speed to get the all core overclock stable on a 12 core xeon.

 

[StereoVsn]

I have tried going heavier into undervolting for 7800x3D, but got tired of messing with it, enabled fairly minimal general settings and called it a day.

Power consumption isnt bad. I am running my RAM at 6000 cl34 (I think) and with a decent 360mm AIO cooler temps go to max low 80s and usually sit at 60s under load. Wasn't worth really deep diving for minor power decrease and very minor performance increase.

 

[JohnnyFootball]

I have tried going heavier into undervolting for 7800x3D, but got tired of messing with it, enabled fairly minimal general settings and called it a day.

Power consumption isnt bad. I am running my RAM at 6000 cl34 (I think) and with a decent 360mm AIO cooler temps go to max low 80s and usually sit at 60s under load. Wasn't worth really deep diving for minor power decrease and very minor performance increase.

Maybe I was just spoiled by what I was able to accomplish with my 7700X.

What I think I am going to try is using Ryzen Master as it was done in this video


Then run OCCT using this method

 

[StereoVsn]

Maybe I was just spoiled by what I was able to accomplish with my 7700X.

What I think I am going to try is using Ryzen Master as it was done in this video


Then run OCCT using this method

If you go ahead with this, please post results here! I am quite interested to see what happens, but probably not enough to spend a day or two trying to tune it just right, lol.

 

[JohnnyFootball]

If you go ahead with this, please post results here! I am quite interested to see what happens, but probably not enough to spend a day or two trying to tune it just right, lol.

Well, I can't use Ryzen Master to fine tune. It seems like you can only support 5000 to actually optimize it in Ryzen Master.

 

[StereoVsn]

Well, I can't use Ryzen Master to fine tune. It seems like you can only support 5000 to actually optimize it in Ryzen Master.

Doh. Maybe it will get updated.

 

[JohnnyFootball]

Doh. Maybe it will get updated.

What it DID accomplish is that it did enable me to identify the best cores. What I am experimenting with is setting Core 2 and 3 at offsets of -10 and -15, while putting all others at -30. I will see what I gain doing that. if anything.

7800X3D hasn't offered remotely close to the amount of thermal improvements that it offered on my 7700X

 

[StereoVsn]

What it DID accomplish is that it did enable me to identify the best cores. What I am experimenting with is setting Core 2 and 3 at offsets of -10 and -15, while putting all others at -30. I will see what I gain doing that. if anything.

7800X3D hasn't offered remotely close to the amount of thermal improvements that it offered on my 7700X

3D cache seems a lot more sensitive to power fluctuations basically. Can't get the crazy power savings like on the main line of 7K CPUs.

 

[peish]

i have 7950x3d, i just set -6 and -12 offset for ccd0 and ccd1, and call it a day. i started with larger negatives, but it crashes randomly, these values are rock stable for a long while.

there's no need to test individual cores for the best negative values each. once you run a fairly heavy loaded app, CPU will apply the lowest/worst offset to all cores.

 

[StereoVsn]

i have 7950x3d, i just set -6 and -12 offset for ccd0 and ccd1, and call it a day. i started with larger negatives, but it crashes randomly, these values are rock stable for a long while.

there's no need to test individual cores for the best negative values each. once you run a fairly heavy loaded app, CPU will apply the lowest/worst offset to all cores.

Yep, that's what I did basically (-10) for 7800x3d. Works fine that way.

 

[SantaC]

I have experience undervolting through PBO. I was running my 7700X with a -30 offset, a max temp of 85C and a max power of 85W and while I lost a little performance temps dropped from 90C to around 61C in Cinebench.


I upgrade to a 7800X3D and it would seem at first to be stable with a -30 offset as well as 85C and 85W powerdraw, but I started getting some game crashes and I ran Cinebench and dropped the offset to -20. It seems fine.
However, the temps are constantly coming close to the 85C. That's fine, as the CPU is (supposedly) designed to handle those temps, but I still feel I can drop them.

Not quite and here is where I am hoping someone with real experience can help.

Well I have been reading that in order to get the most out of your system. You need to really have each core do it's own offset with the highest performing cores having the least undervolt. I have also read the Cinebench is not the best indicator of stability as undervolting stability issues more come into play at idle loads.

My question to anyone with experience, how do you go about finding the best performing cores and how do you go about testing individual configurations. I get that it's not likely a quick process, but I am inspired to play around with it to have the quietest fastest system possible.

My main focus is keeping the temps as low as possible with minimal loss in performance.

Thanks!

Tjmax on 7800x3d is 89c, after that it throttles.

I had your same problems until i decided that the cpu was not allowed to go over 80C. I enabled this is PBO settings (called level 2 80C)

After i enabled lvl2, i put all cores back to 0 and my stability problems were gone while i got the same cinebench score.

 

[JohnnyFootball]

Tjmax on 7800x3d is 85c, after that it throttles.

I had your same problems until i decided that the cpu was not allowed to go over 80C. I enabled this is PBO settings (called level 2 80C)

After i enabled lvl2, i put all cores back to 0 and my stability problems were gone while i got the same cinebench score.

TjMax is actually 89C. A 4C difference might not seem like but that is actually a 39 degree difference in freedom units. Basically, I have it set to throttle.

My first test, thermal limit was kept at its Tjmax (89C) with the my best cores at -10 and -15 and everything else set to -25.
After that appeared to be stable.

I dropped the -25 cores to -30 and set the temp max to 85C. I ended up losing about 150 points in Cinebench. I ran OCCT and everything seems to check out.

My conclusion is at this moment, that the 7800X3D just simply is much more finely tuned such that there is little improvement by undervolting.

I, however, have not checked to see what the power draw differences are. Quite frankly, I don't know how I would go about doing that.


I guess, in some ways it's good that if I get issues with stability I certainly can just run everything at stock and not feel bad about it. I will call it a day. I was really hoping to get a slightly higher booster clock and have my temps never go above 70C on my 7800X3D when doing stress testing.

Unlike my now sold 7700X, I will not sacrifice performance to improve the thermals. Running my 7700X with an all core -30 and an 85W power limit and a 85C cost me some minor performance, but I felt that was worthy trade off since it dropped my temps from 90C down to 61C.

I bought the 7800X3D to get maximum game performance and if the only way to get that is for the CPU to hover between 80-90C then so be it. In gaming I only rarely reach those temps.

 

[SantaC]

TjMax is actually 89C. A 4C difference might not seem like but that is actually a 39 degree difference in freedom units. Basically, I have it set to throttle.

My first test, thermal limit was kept at its Tjmax (89C) with the my best cores at -10 and -15 and everything else set to -25.
After that appeared to be stable.

I dropped the -25 cores to -30 and set the temp max to 85C. I ended up losing about 150 points in Cinebench. I ran OCCT and everything seems to check out.

My conclusion is at this moment, that the 7800X3D just simply is much more finely tuned such that there is little improvement by undervolting.

I, however, have not checked to see what the power draw differences are. Quite frankly, I don't know how I would go about doing that.


I guess, in some ways it's good that if I get issues with stability I certainly can just run everything at stock and not feel bad about it. I will call it a day. I was really hoping to get a slightly higher booster clock and have my temps never go above 70C on my 7800X3D when doing stress testing.

Unlike my now sold 7700X, I will not sacrifice performance to improve the thermals. Running my 7700X with an all core -30 and an 85W power limit and a 85C cost me some minor performance, but I felt that was worthy trade off since it dropped my temps from 90C down to 61C.

I bought the 7800X3D to get maximum game performance and if the only way to get that is for the CPU to hover between 80-90C then so be it. In gaming I only rarely reach those temps.

I got 18300 score in cinbench 23 using my method. What you got?

 

[JohnnyFootball]

I got 18300 score in cinbench 23 using my method. What you got?

17687.

 

[SantaC]

17687.

You should score higher

 

[Brock2621]

Just grabbed this CPU, bookmarking this thread for sure