Question XFR vs Manual OC

Jun 6, 2019
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So AMD's XFR and Precision Boost can increase the core frequency and voltage according to factors like CPU temp, VRM temps and others, why would you still want to overclock a Ryzen Cpu?
I mean.. When you manually oc that's exactly what you look for: core clock as high as possible, while maintaining low voltage and temps. Which is exactly what XFR does. So why would you still need to oc if XFR already does that?
Is there any benefit on doing both manual OC and XFR & Precision boost? I'm talking mainly gaming (single core performance)
 

theterk

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Well, Precision boost bumps up the overclock even further by increasing voltage and frequency while staying within thermal constraints of the system. With PBO enabled, you can go to the maximum that the motherboard (or you) have specified.

The downside with that is sometimes the voltage is too high (up to 1.45V in my testing) which could cause longevity problems. Also, with sustained workloads, the system basically goes back to stock because the power/thermal conditions won't let it continue to boost.

Here's my video stream I did explaining PBO. I can dive more into detail in the future. What is PBO, and can it beat a traditional OC
 
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junglist724

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Well, Precision boost bumps up the overclock even further by increasing voltage and frequency while staying within thermal constraints of the system. With PBO enabled, you can go to the maximum that the motherboard (or you) have specified.

The downside with that is sometimes the voltage is too high (up to 1.45V in my testing) which could cause longevity problems. Also, with sustained workloads, the system basically goes back to stock because the power/thermal conditions won't let it continue to boost.

Here's my video stream I did explaining PBO. I can dive more into detail in the future. What is PBO, and can it beat a traditional OC
I wouldn't say that the voltage is too high, it's really high but it only keeps it that high at low loads and Zen can adjust voltages faster than you can monitor them. PBO has a "FIT" parameter that protects the CPU from degrading. It's more likely that you'll degrade the CPU with manual overclocking.
 

junglist724

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Where did you read that?
https://forums.anandtech.com/threads/ryzen-strictly-technical.2500572/page-72#post-39391302
In order to get the most accurate answer for this question I ended up “asking” the CPU itself. As stated previously, the CPU features various different limiters / safe guards (Package Power Tracking: PPT, Thermal Design Current: TDC, Electrical Design Current: EDC, thermal protection and FIT).

“FIT” as the name suggest is a feature to monitor / track the fitness of the silicon and adjust the operating parameters to maintain the specified and expected reliability. Many semiconductor manufacturers utilize such feature to eke out every last bit of performance, in an ERA where most of the semiconductors are process bound in terms of performance. In short: FIT feature allows the manufacturers to push their designs to the very limit out of the box, without jeopardizing the reliability of the silicon. A practical example would be the knock sensors on an engine. The control unit of the engine always tries to advance the ignition timing as much as possible, to produce the best possible power / torque figures. The purpose of the knock sensors is to listen if knocking occurs and tell the ECU to reduce the timing advance when it does, in order to protect the engine.
It seems to work pretty well since the max safe voltage that overclockers suggest is exactly the same voltage that PBO limits you to on 100% all core loads as long as temperatures are 70C or lower.
 
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theterk

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ehh, I could argue either way. I would say, that with a manual overclock, you know for certain what voltage/frequency you're running and can weigh the pros/cons of where you set it. With PBO, you are left to the firmware and overclocking criteria by software which could overvolt even on low load scenarios. the prolonged workload benefit from PBO is minimal (in my testing) whereas I can see sustained performance increases with a manual overclock.

Another reason why "Boost clock" and "Game clock" has me suspicious that marketing teams are starting to get a little too optimistic with their numbers.
 

junglist724

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@junglist724 do you know who "The Stilt" is? Just curious if he was some famous overclocker or something, or maybe someone well known in the enthusiast community.
Yeah he's a fairly well known extreme overclocker and he's partially responsible for Asus's implementation of performance enhancer lvl 3 and 4 so he's gotten a good look at the bios. Asus also includes his memory timing presets in the C7H bios.

ehh, I could argue either way. I would say, that with a manual overclock, you know for certain what voltage/frequency you're running and can weigh the pros/cons of where you set it. With PBO, you are left to the firmware and overclocking criteria by software which could overvolt even on low load scenarios. the prolonged workload benefit from PBO is minimal (in my testing) whereas I can see sustained performance increases with a manual overclock.
PBO logic is basically all taken care of by the CPU itself and it uses the CPU's onboard voltage and temp sensors so it doesn't really matter what the BIOS or Ryzen Master do since all they do is report max power/current limits to the CPU with PBO on. Even if you change LLC levels the CPU will just change the VID to compensate and get the same voltage at the CPU SVI2 TFN sensor. If you add a voltage offset to overvolt or undervolt the CPU will just drop the VID until the voltage at the cpu is safe(when overvolting) or raise the VID up to a max of 1.55v until the cpu is stable(when undervolting). Even the SVI2 TFN sensor doesn't tell you the whole story because within a die Zen can feed different voltages to each of the cores. AMD knows how their silicon behaves better than us so I wouldn't worry about precision boost overvolting. The cpu can even change voltages/frequencies 2000x faster than hwinfo's default checking interval and 100x faster than the fastest checking interval allowed.

I also saw better performance for all core loads with manual overclocking on my 2950x @ 4.2GHz, but my temperatures were going above 75C over extended loads. The problem is that on 12nm it's not just voltages you have to worry about. People have seen degredation at 1.38v @ 60C and PBO itself will throttle back voltage bit by bit for every degree over 70C so temperature is just as important as voltage on 12nm. I'm extremely wary about setting a manual OC unless using well under 1.375v to give myself some headroom because 1.375v@70C is right on the edge of what ambient cooling can sustain so all it takes is some higher than average ambient temperatures to make your OC unsustainable at max load.
 
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@junglist724 do you know who "The Stilt" is? Just curious if he was some famous overclocker or something, or maybe someone well known in the enthusiast community.
Yes he is famous in OC community for some time now. Has good connections to AMD and Asus. Obviously privy to their secrets. There's also another guy, authority on Ryzen that wrote this program https://www.techpowerup.com/download/ryzen-dram-calculator/ as he was working for Asus at BIOS development.
 
Yeah he's a fairly well known extreme overclocker and he's partially responsible for Asus's implementation of performance enhancer lvl 3 and 4 so he's gotten a good look at the bios. Asus also includes his memory timing presets in the C7H bios.


PBO logic is basically all taken care of by the CPU itself and it uses the CPU's onboard voltage and temp sensors so it doesn't really matter what the BIOS or Ryzen Master do since all they do is report max power/current limits to the CPU with PBO on. Even if you change LLC levels the CPU will just change the VID to compensate and get the same voltage at the CPU SVI2 TFN sensor. If you add a voltage offset to overvolt or undervolt the CPU will just drop the VID until the voltage at the cpu is safe(when overvolting) or raise the VID up to a max of 1.55v until the cpu is stable(when undervolting). Even the SVI2 TFN sensor doesn't tell you the whole story because within a die Zen can feed different voltages to each of the cores. AMD knows how their silicon behaves better than us so I wouldn't worry about precision boost overvolting. The cpu can even change voltages/frequencies 2000x faster than hwinfo's default checking interval and 100x faster than the fastest checking interval allowed.

I also saw better performance for all core loads with manual overclocking on my 2950x @ 4.2GHz, but my temperatures were going above 75C over extended loads. The problem is that on 12nm it's not just voltages you have to worry about. People have seen degredation at 1.38v @ 60C and PBO itself will throttle back voltage bit by bit for every degree over 70C so temperature is just as important as voltage on 12nm. I'm extremely wary about setting a manual OC unless using well under 1.375v to give myself some headroom because 1.375v@70C is right on the edge of what ambient cooling can sustain so all it takes is some higher than average ambient temperatures to make your OC unsustainable at max load.
Normally. over voltages (at or above 1.5v) are very short and transient, not long enough to heat up CPU, you're right about heat. it will degrade or even kill CPU if too high for long time. With Ryzen, xfr is there to correct core voltages according to (inside) temperatures so they don't exceed AMD set maximums unless you force them too high. AMD recommends up to 1.425v at 75c maximum long term values. Unfortunately some BIOS versions push voltages to 1.5v or higher if left to own devices, all in the name of stability.
 

junglist724

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AMD recommends up to 1.425v at 75c maximum long term values.
That was only for 1st gen Ryzen, AMD's kept completely silent about safe overclocking voltages for 2nd generation. Buildzoid and other overclockers don't recommend anything higher 1.375v for a daily OC on 12nm.
 
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