Computer

This is why AMD CPUs consume little power, are they limited?

Densities of millions of transistors per mm2 apart, it is important to understand that AMD and Intel seek to provide processors with maximum performance but within a fixed limit of power consumption, which is more and more specific. This leaves a narrow margin for maneuver where the processor has to move with the operating system looking at what, when and how it does any process as well as the load it receives.

The problem is the triangle (loving if you want to be romantic in hardware) between energy, frequency and temperature. You need a balance that allows you to scale performance without compromising and this is a daunting task that also has to be simple for the operating system. That’s where the P states and frequency hops were born, so from now on we will focus on AMD to understand a little more how the Package Power Tracking or PPT.

Why is energy so important now?

For the same reason we just explained, for efficiency, but let’s give it another twist to understand the energy issue. In the past and although today it can also be done in processors, if the processor overheated it was synonymous with a high voltage or a high frequency, so by adjusting one or both parameters downwards we could reduce the temperature.

But this was an overly simplistic approach, since the performance drain is much greater thus limiting the total power consumption of the CPU. Are they not linked? Yes, but they are not the same nor does it work the same way. When you are competing for every point in a benchmark or for every watt in a CPU to equally maximize performance you cannot afford to lower frequency, and the undervolt only affects the CPU and its voltage.

The solution is to directly limit energy consumption and this is where our protagonist comes in.

What is Package Power Tracking or PPT on AMD CPU?

AMD-PBO

The more or less literal translation of the term would be something like Tracking the power of the packet (of the socket). The feature is almost described by its own name and it is nothing more than the fact that AMD puts a limit on the power a CPU can consume through the motherboard’s rails and power phases.

Here you have to bear in mind that as a good rule it has limits. The first one refers to processors with TDP of up to 105 watts or higher if necessary, the second does the same but with 65 watts. The function is to limit the delivery of energy for the first in until 142 watts being this limitation of 88 watts for the latter (+ -1% margin or GAP according to the phase system of the plate).

This is important depending on the processor to be analyzed, since those that are really close to the limit values ​​in full will be able to scale their frequency more by the algorithm of PBO which is automatic, while those that exceed the 142 watts and 88 watts respectively they will see their frequencies limited and they will touch those consumptions constantly, but they will not be able to go up from there.

Why is AMD limiting its CPUs with PPT?

AMD Ryzen 5000 XT PPT

Because it aims to offer a higher temperature, performance and efficiency ratio. As we have said, everything revolves around efficiency and leaving free the consumed watts or setting very high limits or for a short time what they do is be less efficient and shoot the temperature.

As expected, if we want to, we can break that PPT limit and let the CPU consume and go up more MHz, with more voltage and gain more performance, but the temperature will also rise above the 70 ºC that AMD implements. Therefore, processors such as the Ryzen 9 3950X or the 5950X always mark values ​​between 140 and 144 watts on average or at peak (it depends on the stress and the ASIC they have) where in no case will they exceed that value if it is not by work and our grace to break the limit suggested by AMD.

So once the PPT limit is broken in BIOS, AMD CPUs have no more limits and can go up until the cooling allows it? No, there are security limits that force the descent to prevent disaster for the sake of processor security, but this will depend on the resulting temperature, since if we use LN2 this limit is very high and we can simply take the silicon to its physical limit .

Interestingly, the PPT limit of AMD is not locked down, that is, in post of the reduction of the consumed power, which is perfect to maintain the highest performance by reducing the consumption and the temperature a lot, since the jumps in the CPU SKUs are more progressive and not as abrupt as a drop in frequency and voltage, so the PBO algorithm is allowed to scale more frequently due to the drop in temperature, maintaining similar performance ranges.

This is what the Ryzen Master software does with its eco mode, only that instead of in BIOS with a program and with only 3 clicks and without leaving Windows, but of course it is more advisable to do it in the UEFI, it will always be more efficient in these terms.

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