Load peaks and capping
Let’s first take a look at the flowing currents. Measurements were taken at rough 20 ms intervals, i.e. around 50 times per second, in order to simulate the load on the supervisor chip of the power supply units (switch-off). We can see that all load peaks in these still quite coarse intervals are capped at 38 A at the latest, which is fine. But if we break it down even further, we will also see significantly higher values.
Nevertheless, we still need to take a look at the voltages, or the product of voltage and current flow. I already wrote that I measured three different power supply connections here, even though all three connections meet again somehow on the graphics card board. What we can now see here as much clearer fluctuations and peaks is due to the power supply unit overvolting a little in places and therefore to the voltage and not the currents. This is due to technical reasons, but is not a problem. However, we can also see that the few peaks of up to almost 520 watts are not caused by the flowing current (graphics card), but actually result from the power supply!
The Torture test is hardly any different, even if you can see the lower peak values and, above all, the drops. The average, on the other hand, actually rises slightly.
If you now add the voltage to the equation, you can see a stronger ripple, which in turn results from the somewhat jittery operating voltage. However, to the power supply’s credit, it must also be said that this affects all current products from all manufacturers and can hardly be avoided.
But because I still want to know exactly, I’ll break the whole thing down even higher and take 20 ms as the total runtime. The intervals of 10 microseconds can still be measured reasonably and we can also see the voltage here as a gray curve, the average value of which is just over 12 volts, but which nevertheless still alternates somewhat within the permissible range. What is striking, however, is that the real capping limit is actually around 40 amps, but this is reduced to the 37 amps measured above on average over the running time
If you then convert this to the power consumption in watts, you get this picture:
I also did the whole thing again for the Torture Loop, where we can admire the regular drops. First of all, the currents again, but with lots of strange, sporadically recurring drops in each rise. It looks like a violent hiccup before the power is really throttled back shortly afterwards.
And then the total wattage again:
Power supply recommendation
Now we come to the point that makes a complete mockery of the expected sensation of exploding power supply units. Even IF you hopelessly overpower the card, nobody really needs ATX 3.0 power supplies over 1200 watts, unless the CPU eats up more than 300 watts. This is really a pure job creation measure for the starving power supply industry and only satisfies the sick imagination of some standardization fetishists. You really have to put it that harshly. So you should always stay below 800 watts, even together with the CPU, if you include the load peaks up to 10 ms. Because that’s what the power supply units still “see”
With this in mind, I would also formulate my power supply recommendation for the XFX Mercury RX 7900 XTX Magnetic Air 24 GB as follows: you should be quite safe with a modern 850-watt gold or platinum power supply, although 1000 watts would certainly not be wrong with a lot of peripherals and OC. But it really doesn’t have to be more than that.
- 1 - Einführung, technische Daten und Technologie
- 2 - Test Setup
- 3 - Teardown: PCB, Topologie und Komponenten
- 4 - Teardown: Lüftersystem und Kühler
- 5 - Teardown: Material-Analyse
- 6 - Gaming Performance WQHD (2560 x 1440)
- 7 - Gaming Performance Ultra-HD (3840 x 2160)
- 8 - Gaming Performance FSR vs. DLSS
- 9 - Details: Leistungsaufnahme und Lastverteilung
- 10 - Lastspitzen, Kappung und Netzteilempfehlung
- 11 - Temperaturen, Taktraten und Infrarot-Analyse
- 12 - Lüfterkurven und Lautstärke
- 13 - Zusammenfassung und Fazit
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