In 2025, there are extremely efficient CPUs from Intel and Apple. Under 5W idle!

The old Intel CPUs were grotesquely inefficient. Every single generation of Raspberry Pi has been well under 5W idle. And just so it's clear, the author is using an old Raspberry Pi 3.

From TFA:

> The RPi 3B’s 19.2 MHz oscillator is physically located near the CPU on the Raspberry Pi board, so by actively controlling CPU temperature, we’re indirectly controlling the oscillator’s temperature.

Also note that the R.Pi can even be further optimised by switching off HDMI.

https://www.pidramble.com/wiki/benchmarks/power-consumption

https://www.jeffgeerling.com/blogs/jeff-geerling/raspberry-p...

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nottorp 13 hours ago | parent [-]

> In 2025, there are extremely efficient CPUs from Intel and Apple. Under 5W idle!

I don't think Intel has any "efficient" CPU that can go passively cooled at load though. Maybe Apple can do it for the low end SoCs.

The Pi 3 can go passively cooled and maybe even without a heatsink at load, but the newer Pis can't. Judging by the progression from 3 to 4 to 5, they will reach P4 levels of heat in the name of speed around ... 7?

> And just so it's clear, the author is using an old Raspberry Pi 3.

Yes, the author has harder problems to solve than what I'm whining about. But my concern is a bit related.

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zokier 4 hours ago | parent | next [-]

Noctua has a cooler that can handle something like 65W-70W CPUs completely passively. https://www.noctua.at/en/products/nh-p1

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heresie-dabord 13 hours ago | parent | prev | next [-]

> The Pi 3 can go passively cooled and maybe even without a heatsink at load, but the newer Pis can't.

The Raspberry Pi 4 can be used without a fan. They are packaged inside keyboards, but both the Raspberry Pi 400 and the Raspberry Pi 500 are passively cooled.

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nottorp 13 hours ago | parent [-]

I have a 4 with a huge ass passive heatsink on at home. It's my minecraft server when I feel like it.

The heatsink is uncomfortable to touch (it's not in a case). Pretty sure it would downclock if i removed it. So it works without a fan, but not without a heatsink (I bet the keyboards have a heatsink for the Pis built in.).

A 3 would have worked fine without any heatsink at all. At least at normal room temperature.

	▲	heresie-dabord 12 hours ago \| parent [-]
		> Pretty sure it would downclock if i removed it. So it works without a fan, but not without a heatsink The Raspberry Pi 4 will throttle performance at 80C (if I recall correctly) but it can work without a heatsink. I have a R.Pi 4 working without a passive cooler in an enclosure and it reports 55C-62C most of the time. > I bet the keyboards have a heatsink for the Pis built in You are right, both models use a heatsink. The PCB is also different, although the respective CPUs are standard Pi 4 or Pi 5. Incidentally, the CPU in the R.Pi 400 has a higher clock rate than the standard R.Pi 4, so it performs better.

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echelon_musk 12 hours ago | parent | prev [-]

> I don't think Intel has any "efficient" CPU that can go passively cooled at load though. Maybe Apple can do it for the low end SoCs.

Does the N100 not fit this criteria?

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heresie-dabord 12 hours ago | parent [-]

The N100 requires active cooling.

	▲	ThrowawayR2 8 hours ago \| parent \| next [-]
		Not necessarily; for example, the LattePanda Iota SBC with an Intel N150 has a passive heatsink option. Also, industrial fanless PCs have around for a long time even for much more powerful x86 processors.
	▲	geerlingguy 11 hours ago \| parent \| prev [-]
		Technically it can work with passive cooling. Just, you need a pretty hefty heatsink in comparison to other SoCs.