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The Raspberry Pi 4 needs a fan

jeffgeerling.com

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Re: The Raspberry Pi 4 needs a fan

#271

Post by michaelt »

tagrun wrote: post #249
klickverbot wrote: post #247

Earlier quoted context omitted.

Physicist here too. What exactly do you disagree with? The parent comment is sound – thermal imaging cameras typically under-read on shiny metal surfaces. Their emissivity/absorptivity at relevant wavelengths is low, and reflectivity is high. Thus, their own Planck spectrum is (approximately) scaled down by their emissivity, and consequently the radiation in the measured MIR band is mostly what is reflected, which te…

Let me try again. Assistant Professor of Physics here (not a grad student). Yes, reflectance of room temperature aluminum at those wavelengths is pretty good (not true for all metals BTW). Yes, this usually makes it hard to distinguish thermal radiation and reflected radiation with metals. What are you trying to say though? That whatever comes off from a metal must always be a reflection coming from somewhere else? >…

  What are you trying to say though?
In the first image in the linked article, the thermal camera picture has a scale at the bottom. On the scale shown white and red are hottest (66°C) and blue and black are coldest (23°C). The CPU is black (23°C), and the PCB directly adjacent to it is white (66°C).

kees99 and klickverbot are saying it's unlikely the CPU is actually 23°C, especially given the author's statement the CPU was around 60°C, and that it's well known taking thermal camera images of things with different emissivities will produce inaccurate results.

kees99 is also saying, given that the thermal image doesn't accurately measure the temperature of the CPU, the article's statement that the metal casing helps isn't really warranted.

Re: The Raspberry Pi 4 needs a fan

#272

Post by qplex »

dangus wrote: post #268
throw20102010 wrote: post #205

Earlier quoted context omitted.

It might be misleading, but it's not uncommon. Apple MacBook Pros have thermal throttled at high loads for the past several years. It has throttled for so long that reviewers were surprised that the latest version seems to be using a decent thermal paste and throttles much less. So if Apple got away with it for years on computers that mostly sold for over $2k, then I think the RPi foundation will probably get away wi…

Just to clarify here, all laptops of reasonably small size throttle. Throttling below base clock is the only problem, and it was only a temporary one that was patched out with new firmware on 2018 MacBook Pros.

I guess the reasonable size is relative.

None of my laptops do this.

The thermal design is basically broken if the CPU overheats and has to throttle to prevent a fire.

Re: The Raspberry Pi 4 needs a fan

#273

Post by the_pwner224 »

dangus wrote: post #269
the_pwner224 wrote: post #229

Earlier quoted context omitted.

If Apple can get away with it then the RPi will also get away with it, but it is still a highly deceptive and fraudulent practice. I spent $2000 on a XPS 15 and peripherals two years ago; if I had known about the thermal throttling I would not have purchased it. Dell literally robbed me of a thousand dollars - had I known that all the 'ultrabook'-style laptops had throttling issues, I would have bought a cheaper and…

All portable laptops throttle. What we are vaguely talking about is a firmware bug in the 2018 MacBook Pro i9 that was patched within the first week of release. It's only a problem if throttling takes them below the advertised base clock under normal conditions. There is absolutely nothing deceptive about this. A gaming laptop is not really a laptop at all by comparison. They still get less than 4 hours of battery li…

> All portable laptops throttle.

> It's only a problem if throttling takes them below the advertised base clock under normal conditions.

Seems like a bit of a contradiction?

Dell said that my laptop would have an i7-7700HQ at 2.8 GHz + turbo to 3.something, and a GTX 1050m.

The laptop Dell sent me behaved like this under load: it goes to the max turbo speed, overheats within a few seconds to a minute, and then throttles to 800 MHz.

It's like if someone advertised a car as having a 280 HP engine, but the engine controller limited it to 100 HP because it had an inadequate cooling system and would overheat at any more load. It is deceptive.

With the laptop, underclocking can fix the CPU throttling - mine can now sustain the max turbo speed forever at 70 degrees. But that's like buying the 100 HP car and modding it to get to 280 - you were sold a faulty product. In the case of the laptop it's fixable in software so that's not as big of a deal, but how many normal people do you think would be willing to mess with their CPU voltages? Or even be aware of the throttling?

Even after underclocking the CPU, I cannot use it at the same time as the discrete graphics card. If I do, the combined heat makes the CPU once again go to 800 MHZ.

Expecting to be able to use the hardware my computer was advertised as having is not having unrealistic expectations.

> I'm a little confused at what's "sturdier" about a gaming laptop as well.

In my experience most gaming laptops are made of metal or thick plastic and seem more durable. I actually had a MSI laptop, it was a tank - like the revered Thinkpads, but better. Dropped it from a few feet and it only got a scratch on the surface.

> A gaming laptop is not really a laptop at all by comparison. They still get less than 4 hours of battery life under load, they're an inch or more thick, they're heavy. Many of them do not fit in backpacks. Gaming laptops are essentially designed for plugged in operation.

That's why I got the XPS 15. Had I known that its performance was a fraction of what was advertised I would have ignored this whole category of deceptive laptops and bought a gaming laptop, even though they have all these downsides.

Re: The Raspberry Pi 4 needs a fan

#274

Post by squarefoot »

Moving the CPU on the other side of the PCB would allow the use of a larger and more efficient heatsink, with no need for noisy fans, save maybe for heavy overclocking. Not to mention metal enclosures or panels which would easily become themselves heatsinks once the board is screwed on them using the right spacers and decent thermal paste. Noise aside, fans have moving parts which can break, especially cheap ones (just about all those used in consumer IT), and that makes them a weak spot; that's why I would avoid them whenever possible until really necessary.

Re: The Raspberry Pi 4 needs a fan

#275

Post by w0mbat »

It would also be prudent to drill some air inlet holes in the case as far from the fan as possible to facilitate airflow. Otherwise you Have the fan sucking on a mostly closed box, which strains the fan and makes it hard to move much air through. The existing holes for ports seem inadequate for this as they look largely blocked.

Re: The Raspberry Pi 4 needs a fan

#276

Post by mlonkibjuyhv »

unixhero wrote: post #207
codesushi42 wrote: post #193

Earlier quoted context omitted.

Fans fail too. The heat dissipated will probably shorten the lifetime of the board. At $35 who cares though? And you have more to worry about from the SD storage. The RPi needs an SSD. :)

Just get an Intel NUC

How's the reliability of those these days? At a previous gig I witnessed about a 15% failure rate within 3 years.

Re: The Raspberry Pi 4 needs a fan

#278

Post by logicallee »

kees99 wrote: post #44

Quote: the metal casing helps spread that heat around It does, to a degree. But that is absolutely not what we are seeing in that IR picture. Shiny bare metal is a mirror at the wavelengths that thermal camera uses. So what you see on thermal image where wifi-module shield and CPU are is reflection of ambient (room) where this picture was taken. Try waving your hand around, you'll see it reflecting there too. To meas…

how about touching a thermometer to it? (granted that is one spot, but I'd think it's most precise of all.)

Re: The Raspberry Pi 4 needs a fan

#279

Post by arpa »

acqq wrote: post #265
arpa wrote: post #254

Earlier quoted context omitted.

Genuinely curious person here. What is the key reason to use photon size instead of wavelenght? To stress the quantifiableness of the radiation being capured by the thermal camera? To be honest it is the first time i've seen photon size semicasually mentioned in a conversation. Then again i only had physics in high school.

> What is the key reason to use photon size Photon size wasn't used. Micron is an unofficial name for 1e-6 m, the lengths of 0.7e-6 m to 1e-3 m correspond to the wavelength of infrared radiation: https://en.wikipedia.org/wiki/Infrared So "those 10 micron photons" there mean "the photons of the radiation with the wavelength of 1e-6 m."

Ah! Makes so much more sense, thanks!

Re: The Raspberry Pi 4 needs a fan

#280

Post by [deleted] »

the_pwner224 wrote: post #273
dangus wrote: post #269

Earlier quoted context omitted.

All portable laptops throttle. What we are vaguely talking about is a firmware bug in the 2018 MacBook Pro i9 that was patched within the first week of release. It's only a problem if throttling takes them below the advertised base clock under normal conditions. There is absolutely nothing deceptive about this. A gaming laptop is not really a laptop at all by comparison. They still get less than 4 hours of battery li…

> All portable laptops throttle. > It's only a problem if throttling takes them below the advertised base clock under normal conditions. Seems like a bit of a contradiction? Dell said that my laptop would have an i7-7700HQ at 2.8 GHz + turbo to 3.something, and a GTX 1050m. The laptop Dell sent me behaved like this under load: it goes to the max turbo speed, overheats within a few seconds to a minute, and then thrott…

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