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3700X questions about PBO limits and performance boost

 
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post #1 of 5 (permalink) Old 07-21-2020, 03:15 AM - Thread Starter
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3700X questions about PBO limits and performance boost

Starting off by admitting I am new and having a hard time understanding PBO even after reading and watching hours of information...


Ryzen 3700X
Asus TUF B450m-Plus Gaming
16gb 3000mhz
Stock wraith prism cooler



Recently just bought a 3700X and looking into having PBO enabled, and since I am new to this I see a lot of people using Cinebench R20 as a benchmark for multi and single core scores.


After testing with PBO enabled (and nothing else) I get a slightly higher CB R20 multi score of 4800-4880 ranging in these numbers and while monitoring with HWiNFO I see my temps are peaking at 82c. I am getting 4ghz on all cores.


After testing with PBO set to "Auto" I realized my voltages stay static at 1.2v on all cores while 3.9ghz is maintaining on all cores but I am getting peaks of only 70c in temp.


I came across this reddit thread: https://www.reddit.com/r/Amd/comment...t_them_all_to/ and he talks about monitoring your PPT, TDC, EDC values and adjusting your PBO settings according to their peaks to essentially just raise them slightly above their limits which in return gives you more performance while lowering temperatures. A lot of people seem to be having success with this. I guess my question is, is doing something like this valid or is it hurting the chip? I don't want to hurt the chip by doing a manual OC or any thing else. As of right now I have everything on default except for DOCP (XMP profile) on the ram.


If I am incorrect about any or all of this, please inform me as I want to learn the best way to maximize the chip without degrading it with too much or too less voltage and heat. Every thing I have been reading about this is just going over my head and I am having a hard time understanding it all and at this point I am considering just leaving everything at stock out of fear of screwing up/degrading my chip and I feel like I am going crazy.


Thank you!

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post #2 of 5 (permalink) Old 07-21-2020, 03:42 AM
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Voltage is not the problem with Ryzen CPU's
You can see at stock they operate with voltages up to 1.48V.

What is important is the amperage it pulls/uses.

At stock and with PBO the more amperage you pull the less voltage will be applied (lowering the max amperage/wattage)

Stock voltages are ofc. safe, PBO should be safe to since the scaler inside the CPU still works (FiR)
A manual OC can override this and is where things can get tricky. (With a manual OC you need to watch voltage/amperage yourself since there is no ceiling)

You can put in PBO limits like 300W PPT, 230A TDC and 230A EDC.
This will make your CPU run full blast but still have auto voltage/amperage scaling.
Things can get toasty though especially with AVX loads like in Prime95. (CB20 not so much)
The cooler you run your CPU the more it will scale up voltage/amperage and frequency to.

To not get a crazy hot running CPU in AVX workloads you can limit PBO settings.
I have a 3700x to and have my limits set to:
124W PPT, 73A TDC and 111A EDC. (scaler X4, +100mhz)
With these settings it runs full blast in stuff like CB20 and games but will reduce heat from AVX workloads like Prime95 alot (also lower frequency ofc.)
It runs CB20 between 4100-4200mhz (5025+ multicore score) and single core boosts can go up to 4450mhz

You can try 124W, 73A, 111A yourself.
Since this doesn't limit CB20 (atleast not for me, might do for you since we have a different cooler) you might still get up to the same temperature as before.
If that is to hot for you then limit these settings a little bit more.

Just have to play around with these settings a little and see what works best for you.

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post #3 of 5 (permalink) Old 07-21-2020, 05:54 AM
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Ryzen 3rd gen, uses fluctuating voltage
Voltage remains an issue, but it can control itself
1.485v as peak limit is no problem only because it doesn't sustain this peak for longer than 10-20ms

PBO unless the scaler is set to do so (see it as a loadline) won't overshoot the max limits
BUT it will override the boosting table, and use far to much constant current ~ which indeed can be dangerous
Optimally in this scenario, FIT would protect it from degradation and cause clock stretching while lowering the actual frequency in the hidden

The reason why PBO can behave better according to polkfan, is because you can limit TDC and EDC to limit constant voltage while remaining with potentially higher voltage to meet a higher boost
But nearly always it will result in less performance, in more heat and so less maximum potential boost

Ryzen 3rd gen does lose after 50c, every 10c about 75-100Mhz of potential maximum boost and so also maximum allcore frequency
Having a hotter system by at least 100mV more costant current thanks to PBO, nearly always resulted in less performance than just disabling it

Where you get more performance is like Farih mentioned, by using the AutoOC feature
shifting the maximum target frequency again a 2nd time does shift the boosting curve,
soo you need to work with the scaler AND limit TDC + EDC to tame the high all-core voltage it takes
If you aren't adjusting the Board limits (where throttling is a good thing) you have a shifted boosting curve and the frequency targets might never be met
= lower performance = AutoOC does "nothing" according to many reviewers

An old strategy is to use PBO with a negative offset, as again PBO does add excessive voltage to "maybe" hit higher boost
It can lead to success with a good offset on all-core workloads, as the potential all-core frequency can increase
But by using a global negative offset, you pretty much destory your boosting behavior

Soo the best way remains to full throttle limit TDC and EDC (TDC at 95-98% while CB20 runs) so it does actually throttle the excessive voltage down
Pairing that with higher peak boost = autoOC
can result in better boosting behavior, but you have to first track your CPU at stock under y-cruncher and similar,
and note down for each of these tests what voltage is applied on stock by the FIT module ~ before you use PBO to only do harm
Uncontrolled PBO has nothing but bad results
Voltage on each of theses tests, better read out with ryzen master - the average and current current
Make a spread sheet and fill it out, later try to match the voltage by lowering EDC beyond the 100% range till the same voltage is applied

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post #4 of 5 (permalink) Old 07-21-2020, 11:46 PM
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All things being equal (power delivery etc,) temperature is the key to best PBO boost, I just vent thru some cooling problems and witnessed some high temps (83c+), not only that frequency dropped but scores dropped like a rock. By the time I slowly got it tamed to under 70c. frequency and scores returned, 71c already made it drop by 100MHz+, 73c by 200MHz+ and that's only for top core, others lost even more.
AMD shouldn't have included stock cooler for 8 core and up Ryzen and at same time advertised 4.4GHz as it's not able to get that performance with it.

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post #5 of 5 (permalink) Old 07-22-2020, 08:10 AM
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Quote: Originally Posted by CabanaBanana View Post
Starting off by admitting I am new and having a hard time understanding PBO even after reading and watching hours of information...
...
I think the reason to use Cinebench is it's a fairly repeatable benchmark that adequately stresses all cores for a decent amount of time and is also reflective of real-world computing work load.

If you're interested in exploring PBO optimizations, go skim through this thread: https://www.overclock.net/forum/13-a...rbo-boost.html . Even if you don't want to exploit the 'edc=1' bug you'll learn a lot about PBO overclocking and it's limitations. One thing to keep in mind is that what you will get is highly dependent on your motherboard and specific CPU so don't expect to get exactly what others have.

As others note: Ryzen is very temperature dependent for it's boosting so even though the stock cooler is adequate, if barely, better cooling helps it stay boosted higher/longer and so improves performance. As you've seen the stock cooling won't keep it very cool especially when you push it with some PBO optimizations. AMD has established a Tjmax of 95C for Ryzen 3000 so it is supposedly 'safe' up to that limit (at which point it will throttle itself hard, btw). IMHO, aside from overclocking memory, and IF, getting a good aftermarket cooler is the easiest and safest way to have positive impact on performance.

It's doubtless not good to operate at or close to T-jMax continuously though. There's a feature in BIOS you can set to establish a temp limit at which BIOS will limit boosting of the processor. Since I use PBO overclocking using the 'edc=1' bug I've set mine to 85C even though it never gets there since I've got my 3700X under a decent enough 240mm AIO.

Nobody can truly know for certain since 7nm process node is still so new but I feel overclocking with PBO is the safest way to go about it (since it leaves the processor algorithm free to adjust Vcore) so long as you don't operate at extremely high temps. From what I've seen the people who've run into verifiable degradation have overclocked conventionally with fixed voltages. If you want to explore optimizing PBO and you're worried about operating temps just be sure to set a limit and you'll still get the performance improvement so long as the processing load isn't pushing temps up too high, at which point the temp limiter will kick in and reduce boosting to keep it cool and safe. And of course: get a good aftermarket cooler so the temp limiter never kicks in!

Last edited by buddywh; 07-22-2020 at 02:52 PM.
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