Question VRM Efficiency of Gigabyte Z790 Aero G

[Timur Born]

VRM Efficiency of Gigabyte Z790 Aero G (all external devices disconnected, no dGPU, no PCIE, no LAN, no lights, fans at 100%, Power Saver profile)

PSU Output (Sum of all rails) at idle: 35 W.
35 W - 4 W(CPU) - 10 W(fans) = 21 W Rest-of-System
PSU Output at 253 W CPU power limit (P95 4K smallest, only L1 cache used): 329 W (and increasing with VRM temperature).
329 W - 21 W(Rest-of-System) = 308 W
253 W / 308 W = 0,82..
VRM Efficiency = ~82%

 

[Timur Born]

So what am I missing here? The FDMF5062 are listed at well over 90% efficiency at 1.8 V in the relevant current range.

 

[solidsnake1298]

RAM, south bridge/chipset, USB controllers, onboard audio, networking controllers (even if unplugged).

Also, for your load calculation you are assuming that the rest of the system stays at 21W. Even with the small PPT Prime95 load, your RAM is still being used and will draw more power.

And you have to take into consideration that motherboard manufactures often ignore the max TDP of a CPU. Especially on the Intel side and even more so on high end boards as a way to justify paying a premium for the high end boards. "Your CPU is faster on our board!!" (at the cost of efficiency and heat)

MCE & CPB Investigation on Intel & AMD | Sneaky BIOS | GamersNexus

stub Multi-core enhancement is an important topic that we’ve discussed before – right after the launch of the 8700K, most recently. It’ll become even more important over the next few weeks, and that’s for a few reasons: For one, Intel is launching its new B and H chipsets soon, and that’ll...

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That is an old GN article about the 8700k, but the concept is still true for the 13900K I'm assuming you have. Your assumption that 253W is the max that CPU will ever draw is flawed.