Question CPU Idle Power Draw Depends on Motherboard?

[jtyubv]

I have an intel i7 8700 (non-K) CPU and I have tested running it in two motherboards.

1. Asus Prime Z390-A motherboard
2. The motherboard in the HP Slimline 290-p0043w system (the Celeron processor that comes with this system by default can be swapped to an i7 8700)

Interestingly, I noticed that the idle power draw of the CPU (as reported in LibreHardwareMonitor and HWmonitor) in the Asus motherboard is much higher, around 10 to 14 watts, while in the HP motherboard, it is only 3.5 to 4 watts.

I don't really understand this happens. Why would the CPU be drawing more power at idle in the Asus motherboard compared to the HP slimline?

This test was done with no graphics cards in either system, only using the onboard graphics with a single 1080p display while sitting at the Windows desktop idle. Only one mouse and keyboard were in the USB ports. The "minimum processor state" in Windows was set to 0% on both systems.

 

[NanoSuit3]

Certain Mobos such as the Z390-A is a board for gaming that allows for OCing with extra power drawing from the wall whereas the HP Slimline 290-p0043w is a basic business headline board that won't draw extra power from the wall to do anything. Seems kind of strange at first but if you access the BIOS on the Prime Mobo you can even OC the 8700 a bit even though it's a Non-K CPU . . . I know this cuz I used to have a Z370-E ROG Mobo in my streaming PC before upgrading it to a Maximus XI Hero-Wifi with a 9900KS so..................by all means question the logic it's all basic facts kiddo.........................

 

[jtyubv]

Certain Mobos such as the Z390-A is a board for gaming that allows for OCing with extra power drawing from the wall whereas the HP Slimline 290-p0043w is a basic business headline board that won't draw extra power from the wall to do anything. Seems kind of strange at first but if you access the BIOS on the Prime Mobo you can even OC the 8700 a bit even though it's a Non-K CPU . . . I know this cuz I used to have a Z370-E ROG Mobo in my streaming PC before upgrading it to a Maximus XI Hero-Wifi with a 9900KS so..................by all means question the logic it's all basic facts kiddo.........................

Shouldn't it only be drawing extra power under load? I don't see why that should impact the idle power draw.

 

[Misgar]

The difference in power draw is probably due to different Southbridge chipsets on the two mobos.

The more professional board may have a more power hungry audio codec, a 2.5GbE Ethernet chip, plus various other semiconductor devices. The CPU is only one of many components drawing power.

Small wonder there's a measurable difference between the two boards.

If you read reviews where they test a number of boards from different manufacturers with a common chipset, you may see the idle power draw mentioned, with some boards pulling an extra 10 to 15W.

 

[thestryker]

The HP system may have more C-states enabled than the desktop board does which means it can shut off more of the CPU. That's the only thing I can think of which would directly cause the CPU itself to report lower power draw unless the clockspeeds were different on each motherboard. No matter what the overall power draw will be lower on the HP setup due to the size of the motherboard and features on it.

 

[TerryLaze]

Certain Mobos such as the Z390-A is a board for gaming that allows for OCing with extra power drawing from the wall

Allow is not the right word here...
They just do it without you even knowing about it.

I don't really understand this happens. Why would the CPU be drawing more power at idle in the Asus motherboard compared to the HP slimline?

Go into bios and upload pictures of the CPU settings, my guess is that it has some sort of all core boost / multi core enhancement.
Might be called CPU Power Enhancement in asus boards.
If the board forces all vores to run at full speed even under idle then they will be drawing more power.