In the pictures I can see only one hole immediately above the fan, but I assume you would need at least an intake and an exhaust? Where is the other one?
The Raspberry Pi 4 needs a fan
241–250 of 293 posts
Re: The Raspberry Pi 4 needs a fan
#242I'm always a fan for RPi4
Re: The Raspberry Pi 4 needs a fan
#243What about a bigger heatsink?
That has been tried to great success with the rpi3, so I suspect it will at least make it less prone to throttling. Edit: I just stacked a bunch of 10sec coins on the processor (without any thermal compound) brought the idle temperature down by 3 degrees C. Edit2: Put an carbon tablet pipe on it, filled with coins. It is not up to heat yet, but right now it is idling at about 45C. It would probably be better with som…
What is 'carbon tablet pipe'? I tried to google it, but nothing useful turns up.
Re: The Raspberry Pi 4 needs a fan
#244Earlier 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…
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…
Whereas I am aware of thermal throttling issues across most thin-and-light laptops, and kept that in mind when purchasing it. I was not defrauded. Perhaps though, I'm more sensitive to it, as I used to write my own throttling scripts for my weird AMD APU "netbook" years ago.
Re: The Raspberry Pi 4 needs a fan
#245Earlier quoted context omitted.
Well the pi3 does not support h265 acceleration natively, it should have been better to use it on h264 movies.
Hardware acceleration comes in degrees... It's totally possible to hand-code some GPU firmware to decode any bitstream far more efficiently than the CPU can do it... It's just a lot of work, and either Broadcom hasn't done it, or they don't want to license it to the Raspberry Pi.
I thought (for some reason, I could be wrong), that hardware acceleration for h265 implies actual dedicated silicon, either in the SoC itself or on the board?
Re: The Raspberry Pi 4 needs a fan
#246This article is actually describing how the Raspberry Pi 4 does NOT need a fan. This is not the 1990s. It is perfectly acceptable and even advantageous to design for a high peak:normal load ratio, with thermal throttling. In this case, it allows for a compact, cheap, fanless design for the vast majority of users. There is no evidence the heat dissipated will impact lifespan. It is common for the components picked out…
> It is perfectly acceptable and even advantageous to design for a high peak:normal load ratio, with thermal throttling.
Thermal throttling is never acceptable. You should be able to peg the CPU at 100% indefinitely without any throttling.
Re: The Raspberry Pi 4 needs a fan
#247Quote: 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…
Physicist here, and I disagree. Where else could that radiation with ~10 micron wavelength at that intensity with that localized spatial profile from that particular direction be coming from? Yes environment typically will have some residual "noise" at those wavelengths, which you can check its intensity and spatial profile by taking a "dark frame" if you're in a strange environment and are really suspicious, but it'…
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 tends to come from the room-temperature environment.
A polished piece of metal makes a shitty black body. This is also why shiny metal (foil) is used to curb unwanted radiated heat transfer everywhere from thermos flasks and cryostats to space probes. (The lower emissivity further improves the efficiency of multi-layer insulation.)
Re: The Raspberry Pi 4 needs a fan
#248Earlier quoted context omitted.
> There is no evidence the heat dissipated will impact lifespan. I have to nitpick at this a little bit as a professional EE who works in high-reliability electronics. Wearout rates absolutely do depend on temperature (and thus heat), and thus the chips used here will have a shorter lifetime than those with active cooling. Now, whether that lifetime will be long enough for the common user is another question (maybe i…
Yes, wearout rate definitely depends on temperature, but without reference to any actual data, this is what I mean by "no evidence". Is it reducing 10 year lifespan to 9 years? 9.99 years? 5 years? Was it 50 year lifespan? It's pointless conjecture.
If the pi is designed to throttle at a temperature where its lifespan is reduced from 50 to 49 years, then it is throttling at a gratuitously low temperature that affects quite a few use cases.
On the other hand, if it is designed to throttle at a temperature that materially reduces the lifespan, then it needs a fan to preserve its lifespan.
Either way, the hardware is starkly suboptimal for a pretty large set of advertised use cases until you add a fan.
Re: The Raspberry Pi 4 needs a fan
#249Earlier quoted context omitted.
Physicist here, and I disagree. Where else could that radiation with ~10 micron wavelength at that intensity with that localized spatial profile from that particular direction be coming from? Yes environment typically will have some residual "noise" at those wavelengths, which you can check its intensity and spatial profile by taking a "dark frame" if you're in a strange environment and are really suspicious, but it'…
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?
> 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 tends to come from the room-temperature environment.
I don't know what you mean by "Planck spectrum is (approximately) scaled down" (as "Planck spectrum" only refers to thermal radiation and is generated in a separate process from reflected photons [one is governed by the conduction band whereas the other is governed by everything up to Fermi level] and you can't hope to suppress thermal radiation by simply shining random environmental light on a metal --there is no such thing as "scaling down" of thermal radiation unless you engineer such property), but there is just no way that 10 micron photons at that intensity could be coming from a room-temperature environment.
So your blanket statements about metals aside, the hot area in that picture is due to a very specific signal which can't be due to something that's reflected from the environment. No significant fraction of those 10 micron photons coming off from that localized the area around the CPU could have originated from the environment --assuming that those pictures aren't taken in a hot oven and someone focused the thermal radiation on to the heatsink to get that amount of intensity.
And as I mentioned, that's pretty trivial to test. If those 10 micron photons were coming from the environment as you or the parent comment suggest, the thermal camera would report ~60C even when you look at Pi 4 when it is cooled (again, this is something can use as "dark frame" and subtract off from all readings if you're trying to be more accurate). This is clearly not the case, though, as you can see in the video on the blog post.
Re: The Raspberry Pi 4 needs a fan
#250Quote: 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…
Understanding the reflectivity and emissivity of the material you are measuring is something that almost nobody accounts for outside of critical, professional applications.
Not that it makes the measurements in question any less inaccurate, but it's very common to see these problems in temperature measurements.