Dell 5591 overheating in memtest86+ but cool running Linux Mint - What causes this?

[honigmann]

This machine comes with the i7-8850H, no internal drive and no battery installed, the bottom cover removed, an original Dell power supply is used. I just installed 8GB RAM, ran memtest86+ and noticed a power draw of about 40-50W. Accordingly within minutes the temperature went up to just below 100 degrees with the fan spinning wildly. Same thing when I enter the BIOS (1.20.0), around 40W power draw.

Next thing I tried was an install stick with Linux Mint on it. Initially I am also at around 40W but with idle desktop (Xfce) it draws just 6,5W. Is this a BIOS issue? Version 1.34 is available and ranked critically. The description does not tell me anything about any power issues. I would need to order a battery to apply the update. Will this solve the problem likely or is there anything else going on here?

[eccerr0r]

computers always use more power when doing something... Running memtest86+ uses a lot of cpu cycles especially for computers whose RAM approaches speed of internal busses, though it's still slower and won't completely max out the cpu.

BIOS setup also tends to be poorly written and won't take advantage of sleep where OS will do. So yes power consumption in BIOS setup tends to be high.

Thus all of this seems normal to me.

[honigmann]

Thanks. I was surprised about the very high temps. Never had a device getting above 95 degrees celsius in memtest86+. Now I tested a Dell E5530 in the same way and got BIOS 24,5 W, memtest86+ 35-40W at 62 degrees, and Mint 24W.
I have ordered a battery and will report in case the BIOS update helps to lower the power consumption.

[eccerr0r]

BIOS update will not lower power consumption in BIOS setup, unless they decide to completely rewrite it which they will not... They figure that most of the time people won't be idling in BIOS setup (why??! just turn the computer off!) so they don't optimize for it whereas being operationally ready in an OS is common.

As far as I know about memtest86+ - which I haven't carefully done power consumption tests - is also likewise not written for power save. It was meant to run the CPU as fast as possible to do ... testing memory, else it would take forever as well as not represent real life situations. Some tests that do xor, etc., probably use more power than ones that just read/write memory, and again as the memory subsystem gets fast enough to feed the busses as fast as the CPU can handle it, the CPU won't have to wait in lower power mode, and will continue to run at full speed.

95°C is hot but not way too out of line for some laptop CPUs... you may want to check cooling.

[honigmann]

You were right. The update did not change anything. The idle desktop of W10 draws around 16W, battery detached, with internal disk.