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12700K at 100C after few minutes of Prime95

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Just offset VCore by -0,05V or -0,1V and check stability.
Decrease all boost frequencies by 100MHz, if it's not stable.
 
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I only meant that running the CPU a high PL2 for periods in the order of a minute or so and then keeping it at a relatively low PL1 for the rest of the computation time makes sense if the intended aim is taking advantage of the "available thermal capacitance". From the datasheet linked earlier:

View attachment 261314

Clearly, they're not referring about core temperature, since it has almost no thermal inertia and reacts immediately to load changes. On the other hand, externally-measured temperatures very close to the CPU itself (e.g. socket temperature as I showed in the image posted the other day) react with speed consistent with the Intel-recommended Tau time.

Of course one might argue that the 240+ watts is an excessively high power draw, even if for short periods. That is a related but different subject.

Say the heatsink is 40 deg C at idle (~15W) and you put 125W to the CPU and the CPU temp went up to 80 deg C.

If the same heatsink (shortly after the CPU was loaded) is 50 deg C at idle (15W) and you put 125W to the CPU at that point, the CPU temp would increase to 90 deg C.

I'm just pointing out they could be talking about this thermal capacitance (I think they are)
 

Rob6502TPU

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I only meant that running the CPU a high PL2 for periods in the order of a minute or so and then keeping it at a relatively low PL1 for the rest of the computation time makes sense if the intended aim is taking advantage of the "available thermal capacitance". From the datasheet linked earlier:

View attachment 261314

Clearly, they're not referring about core temperature, since it has almost no thermal inertia and reacts immediately to load changes. On the other hand, externally-measured temperatures very close to the CPU itself (e.g. socket temperature as I showed in the image posted the other day) react with speed consistent with the Intel-recommended Tau time.

Of course one might argue that the 240+ watts is an excessively high power draw, even if for short periods. That is a related but different subject.
I see, I assumed you knew that PL2 was allowed for the whole duration of the heavy load, which is why the 100C thermal limit is hit and maintained on well optimised software using the CPU to max.
 
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Say the heatsink is 40 deg C at idle (~15W) and you put 125W to the CPU and the CPU temp went up to 80 deg C.

If the same heatsink (shortly after the CPU was loaded) is 50 deg C at idle (15W) and you put 125W to the CPU at that point, the CPU temp would increase to 90 deg C.

I'm just pointing out they could be talking about this thermal capacitance (I think they are)

125W would be a load within the processor's stated TDP. If the cooler is only sufficient enough not to cause thermal throttling at the TDP (minimum requirement by Intel), it is virtually guaranteed that the CPU will hit almost immediately the thermal throttling point at a significantly higher load. Even on my Noctua D15S, when a load of say 200W is applied, reported core temperature jumps from ~40 °C to 90°C within 2-3 seconds and reaches the thermal throttling point soon after that.

Cooler temperature however rises much slower than core does. And IHS temperature (Tcase), which unlike core temperature is part of the thermal specifications for lidded CPUs, can be expected to be close that of the cooler near its base, perhaps at a heatpipe. For this, a Tau time of 28~56 seconds as recommended does make sense.

The thermal specifications don't say that the CPU cannot be at the throttling point during the limited time at PL2 (or anyway at a power greater than PL1/TDP), only that core temperatures should be below TJmax when the CPU is at TDP, and that TCase should be below specification values. So the thermal behavior I showed the other day seems acceptable and within specification, in my opinion.

I see, I assumed you knew that PL2 was allowed for the whole duration of the heavy load, which is why the 100C thermal limit is hit and maintained on well optimised software using the CPU to max.

PL2 has always been intended to be limited in duration in the datasheets, not to last for the entirety of the heavy load (a rendering job could last hours or days or more, that seems excessive at PL2).

Alder Lake launch slides did mention that PL1=PL2 brings the best CPU performance, but that doesn't seem to be an official recommendation. So, what to trust? Datasheets or marketing slides?


1663066950947.png 1663067602611.png
 
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125W would be a load within the processor's stated TDP. If the cooler is only sufficient enough not to cause thermal throttling at the TDP (minimum requirement by Intel), it is virtually guaranteed that the CPU will hit almost immediately the thermal throttling point at a significantly higher load. Even on my Noctua D15S, when a load of say 200W is applied, reported core temperature jumps from ~40 °C to 90°C within 2-3 seconds and reaches the thermal throttling point soon after that.

Cooler temperature however rises much slower than core does. And IHS temperature (Tcase), which unlike core temperature is part of the thermal specifications for lidded CPUs, can be expected to be close that of the cooler near its base, perhaps at a heatpipe. For this, a Tau time of 28~56 seconds as recommended does make sense.

The thermal specifications don't say that the CPU cannot be at the throttling point during the limited time at PL2 (or anyway at a power greater than PL1/TDP), only that core temperatures should be below TJmax when the CPU is at TDP, and that TCase should be below specification values. So the thermal behavior I showed the other day seems acceptable and within specification, in my opinion.

I completely agree what you described is in spec.

My point wasn't 125W, my point was the action. Whether that be at 65W or 250W.

I do get why you take issue with me using 125W for the example though - I should've used a value over TDP.

Delta - the difference between two values.

Think of the delta between CPU temperature and heatsink temperature. For example, if 200W creates a 50 deg C temperature delta and the heatsink is cooled to a temperature of 40 deg C at idle, the second you apply 200W, the CPU temperature rises to 90 deg C.

Now think, with 200W, how fast does the heatsink rise in temperature with the fan at 100%? If it's 5 deg C per minute, you have 120 seconds until thermal throttling occurs. As long as so much power isn't added that the delta is 60 degrees (instantly causing the CPU to hit 100 degrees), the CPU is fine thermally - Turbo Boost 3.0 I believe is the one which dictates you can do anything to the CPU up to that point, up to anything that doesn't exceed maximum current obviously

Ideally you have a cooling solution which is able to keep up with any real world load you apply to the CPU so that you never run into thermal throttling.


Side note: For these huge powers that are being allowed lately, I don't think it's a good thing for chip longevity - thermal cycling causes growing and shrinking of the loaded parts of the die, which over time is bad for connections between parts
 
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What I'm implying above more in general is that when the Intel-recommended PL2 can even be more than 3 times the PL1/TDP value, thermal throttling should be expected when the CPU is boosting above the TDP, in particular if mated with a cooler of its TDP class.

For instance, the 65W (non-k) 12900 has a PL2 of 202W. The previous 65W 11900 had an even higher PL2 of 224W. The boxed coolers they came with couldn't possibly dissipate such power for more than a few instants—much shorter than their Tau time—and would certainly cause the CPU to operate at TJMax until the limited boosting period expires, while CPU power slowly decreases due to the throttling.

However, thermal throttling, when operating under standard settings (dynamic voltages/frequencies), isn't necessarily a critical condition. The CPU will typically very gradually decrease frequencies and voltage to prevent internal temperatures from exceeding the limit, with no perceivable stuttering behavior that perhaps might have used to occur in the past, which made people try to avoid it at all costs. I'm currently running my 12700K with a 90 °C limit (it's configurable within a limited range on Z motherboards), which causes it to thermally throttle earlier and more also with real-world workloads (Blender, etc). There are no practical drawbacks that I can see except obviously that on average frequencies under full load will be lower and decrease quicker.

Of course (again), under standard settings it can be argued that CPU longevity could be negatively affected with frequent intense thermal and power excursions. Constant operation at the thermal limit is definitely not recommended by Intel, but they seem to be ok with these CPUs operating at high power and die temperatures for short periods of time. We'll see in a few years if they will start dying earlier compared to their predecessors.
 

Lei

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Just curious for others like myself despite fixing limits that still hit 100c during prime95, what program did you end up using to ultimately determine if the cpu is stable in the long run as a result?
I use Argus monitor. It automatically turns the pc to sleep if cpu reaches a certain temp.
So I can peacefully take shower and leave the PC on.

I have an exe file that sleeps the PC, argus runs it when it hits a high temp (instead of sending me an email lol)
 
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