9 ms·

Raspberry Pi Zero 2 W die shots

190 points by geerlingguy 5y ago

rwmj 5y ago
What is the silicon spacer used for? And where is it located - there's not a picture of the three pieces of silicon in the package. Also fun to see this next to the 8086 die shots. How things have progressed in 40 years.
- mkoc 5y ago
  have a look here [0], Fig 1; the spacer serves really as a mechanical spacer (if dies are same or similar size); also nice for heat spreading. [0] https://www.semanticscholar.org/paper/Productivity-improvement-of-stack-package-line-die-Jin-Li/bd8bc2ea571d8e898ce74aa1d107d20fd035dbff https://www.semanticscholar.org/paper/Productivity-improveme...
- magicalhippo 5y ago
  You can see an illustration of the RP3A0 system-in-package in the official blog post[1]. From what I can gather[2] the spacer is actually an interposer, which for all intents and purposes functions as a PCB between the two chips, allowing for signals to be routed between the chips. Think of it as two IC's on either side of a PCB with vias connecting them. No expert though so maybe I'm mistaken. [1]: https://www.raspberrypi.com/news/new-raspberry-pi-zero-2-w-2/ https://www.raspberrypi.com/news/new-raspberry-pi-zero-2-w-2... [2]: https://sst.semiconductor-digest.com/2011/06/silicon-interposers-building-blocks-for-3d-ics/ https://sst.semiconductor-digest.com/2011/06/silicon-interpo... (section "Alternative 3D technology")
  - deleted 5y ago
    [deleted]
  - magicalhippo 5y ago
    I was assuming they called it an interposer for a reason. However as the sibling comment by mkoc mentions it might just be a spacer, and the X-ray image[1] of the package seems to confirm that. [1]: https://www.jeffgeerling.com/blog/2021/look-inside-raspberry-pi-zero-2-w-and-rp3a0-au https://www.jeffgeerling.com/blog/2021/look-inside-raspberry...
bigbaguette 5y ago
Between the pictures of the 8086 from 40 years ago and this, it makes me wonder what die shots will look like in 2060. Will we be slicing compute cubes?
- vbezhenar 5y ago
  We're using 2D schemes because we live in 3D world and we can move heat into third dimension. With 3D circuit you won't be able to transfer heat from the insides. I guess it could be possible with some integrated cooling nano pipes, but it's hard to imagine how that would work.
  - FrostKiwi 5y ago
    Many pieces of circuitry on different scales are already 3D. On the big side, PCBs are printed in multiple layers, going smaller we have 3D NAND flash, micro processors are very much printed in "layers" with components being connected "one story up" and those layers are again connected "two stories above". Finally you might argue on the atomic scale, individual transistors are very much 3D as well, with how source, gate and drain are constructed. But I get your point, you can't just stack those layers ad infinitum.
    - deleted 5y ago
      [deleted]
  - Causality1 5y ago
    Always been fascinating to me that we only bolt a heat sink onto one side of the board. Nobody's come up with a circuit board material that's electrically insulating but thermally conductive so we could sink an appreciable amount of heat out of the back side?
    - CamperBob2 5y ago
      Interestingly, thermal and electrical conductivity is highly correlated. You don't see a lot of materials that conduct heat well but behave as good electrical insulators, or vice versa. Both mechanisms benefit strongly from the availability of highly-mobile electrons, which is another way of saying "metal."
blamazon 5y ago
> When one codes on a Raspberry Pi one generally thinks of these CPUs as the core of the device with all the peripherals surrounding them... however the provenance of this chip is much more interesting and the CPUs are actually an afterthought. > The primary design goal of this chip was for cable TV set top boxes. For that the designers focused on transporting video. The real core of this chip is the "Video Core IV".... it's the actual master.
- geerlingguy 5y ago
  And fun fact: when the Pi boots up (all generations so far), the primary bootloader is the VPU (VideoCore), which then initializes the CPU and RAM. These things are slightly weird in that way.
  - riobard 5y ago
    What does the VPU do after boot if the unit is headless?
    - deleted 5y ago
      [deleted]
    - sydney6 5y ago
      E.g. accelerating video decoding/encoding, OpenGL applications, etc..
    - magicalhippo 5y ago
      Well you could use it for GPGPU[1], for example[2]. [1]: https://www.cnx-software.com/2019/10/10/py-videocore6-raspberry-pi-4-gpgpu-python-library-videocore-6-gpu/ https://www.cnx-software.com/2019/10/10/py-videocore6-raspbe... [2]: https://github.com/Idein/py-videocore6/blob/master/examples/sgemm.py https://github.com/Idein/py-videocore6/blob/master/examples/...
syntaxing 5y ago
It never ceases to amaze me that someone can look at these die pictures and knows what’s going on. All I see is a bunch of copper colored squares
- 60Vhipx7b4JL 5y ago
  after some time it's fairly easy. E.g. if you know it has a 4 core cpu, you're just looking for the same area four times.
- MisterTea 5y ago
  Its not far off from looking at a circuit board and recognizing layout patterns and chip shapes to get a feel for whats going on. e.g. Larger chips are usually of interest. A larger chip with one or more little rectangular chips next to or surrounding it is likely the CPU and RAM/Flash/ROM. Smaller chips are interface or power regulators depending on their proximity to ports and other components. Groups of inductors, capacitors and transistors are likely power supplies. It all comes with experience.
- hobs 5y ago
  I honestly thought being able to recognize ground up spices by eye was an amazing feat until I started cooking more than once a month.
- stavros 5y ago
  You develop your intuition by looking at (or designing) a lot of these. It's like any other profession, I guess, experience makes pattern matching easier.
skywal_l 5y ago
> It might grate on some hobbyists who see this secretive approach as the antithesis of open-source but Google Broadcom's stock price and one can see it's been a fabulously successful company. I am really interested to see what the people on HN will make of this statement.
- LeifCarrotson 5y ago
  I think the two factors being compared - open vs. proprietary, poor vs. wealthy - are orthogonal to each other. Does the author imply that open-source advocates believe that secrecy is bad for profits and that open-source is a way to get rich? I've not personally heard that. I do recall arguments that opening your source code will not lead to financial ruin, but that still leaves open the possibility that they're uncorrelated or only weakly correlated.
  - salawat 5y ago
    Broadcom, as I understand, is as secretive as they are as a defense against patent trolling. When you have NPE's gobbling up garbage patents to sue everyone and their brother with, locking up the IP tightly is one adaptation to defend against that sort of thing. Still pisses me off to the ends of the earth.
- Buttsite 5y ago
  He sounds like a total moron because the next paragraph talks about how that secrecy lead to this chip being used for cable sets instead of computers until the Raspberry Pi. But pushing back the state of the art must be worth it for the stock price!
  - geerlingguy 5y ago
    I think the main reason nobody else picked up these chips was because they're not really made for general purpose computing. Rather, many of the Pi engineers come from Broadcom, so it was probably more familiarity, price, and partnership that were the main drivers for it getting popular on the Pi.
- 5y ago
admin786 5y ago
Thanks for visiting
Namidairo 5y ago
> The only downside is that external light can actually affect the chip operation (light hitting the die releases electrons at PN junctions creating errors in circuit operation ) .. .however here the Faraday metal shield helps prevent this. Brings me back to when it was discovered that high intensity flashes could make a Raspberry Pi 2 reboot...[1] [1] https://www.raspberrypi.com/news/xenon-death-flash-a-free-physics-lesson/ https://www.raspberrypi.com/news/xenon-death-flash-a-free-ph...
- squarefoot 5y ago
  Many PN junction based components such as diodes and transistors are photosensitive; I recall after reading this as a kid on an old electronics magazine, I took a 2N3055, a pretty common power bipolar transistor back then, uncapped it to expose the die then connected it to my analog tester and saw it generating current when exposed to a lamp. The effect is common also in devices one could never suspect to be sensitive to light such as LEDs. They can produce light but also detect it. A few years ago someone published a project online of a MCU based keyboard (actually a button board) made of PWM driven LEDs that can both produce light and during their off cycle detect it, so that one turns them on and off just by touching them with a finger screening them from surrounding light. I attempted to search for that project without luck.
  - daniel_reetz 5y ago
    I remember that project too. Might have been Paul Dietz at MERL.If you're curious, look up Paul Dietz "low cost bidirectional sensing using LEDs" and Forrest Mimms "LED Sun photometry".
    - jacquesm 5y ago
      > Forrest Mimms There's a name I haven't seen in a long time. Source of endless insight into electronics parts and schematics.
      - avhon1 5y ago
pixelpoet 5y ago
> Taking the die off the board and flipping it over reveals the typical beauty of an RF design. Knowing basically nothing about electrical engineering, what does this refer to?
- moffkalast 5y ago
  RF would stand for radio frequency I guess, so I suppose it's the wifi module or something.
- geerlingguy 5y ago
  Not an RF engineer, nor even electrical engineer, but from what little I know, if you think computer networking is voodoo magic (as I do), RF design (especially in tiny couple-mm-square chips) is like black arts mixed with ancient mythology. RF does weird things, and controlling it so it can be useful for high speed networking in the wacky environments where we put computers is IMO a pretty big feat of modern engineering. But the chip design is just pretty in its own right, with the layers coming through.
  - pixelpoet 5y ago
    Thanks for the explanation, and love your videos BTW!
- GeorgeTirebiter 5y ago
  RF usually has not too many transistors, but sometimes a lot of coils and capacitors. You can see the coils in the design, somewhat snake-like. Capacitors can be realized in many ways, conducting material over a dielectric. Bulk capacitors are external (as you can see). Matching LC are external because those depend on the antenna; I'm a little disappointed there wasn't more detail given of the antenna, because this type I believe is a 'first' for the RPi 'in-board' antennas, in that they have two lines of series-connected capacitors inside the 'triangle'. I don't yet know how this works. RF ICs are usually hand-routed, too. So you get to see some real 'Art'.
  - pixelpoet 5y ago
anonymousiam 5y ago
Nice photos! Off topic, but has anyone else noticed the scarce availability of the "regular" Raspberry Pis? A few can still be purchased at a premium price, but many vendors have no stock. Some vendors (such as Element 14) claim a backlog until 12/2022!
- teh_klev 5y ago
  The PiHut (UK) seem to have a pretty good stock of Pi 4 Model B's, though admittedly just the 4GB and 8GB variants: https://thepihut.com/products/raspberry-pi-4-model-b https://thepihut.com/products/raspberry-pi-4-model-b I picked one up just recently from them with no delays.
- tmaly 5y ago
  I just tried looking for the zero 2 W. All the sellers on the main raspberry pi site are completely sold out till next year. I managed to score the last 2 on digikey.
- bliteben 5y ago
  I got a 4gb recently from vilros with no real delays.
  - anonymousiam 5y ago
    Well, I searched OctoPart last week and found only a few vendors with stock, and all of those were for the "kit", which includes some useful accessories that I don't need, and raises the price by about $25. Also, all of the Pi4b stock was for the 4GB version. No 8GB Pi4bs anywhere on OctoPart. So last week I ordered two Pi4b 4GB kits from Allied for $90.61 each. The last Pi4b (8GB) I bought was $75 from Newark/Element 14 in January. Amazon is now selling the 8GB Pi4b for $160.
- aVx1uyD5pYWW 5y ago
  https://www.raspberrypi.com/news/supply-chain-shortages-and-our-first-ever-price-increase/ https://www.raspberrypi.com/news/supply-chain-shortages-and-...
echoradio 5y ago
Am I seeing this right, that the contacts underneath the plastic housing for the chip are patterned like the Raspberry Pi logo?
- georgemcbay 5y ago
  Yes. It is intentional. They mentioned this in the product announcement: https://www.raspberrypi.com/news/new-raspberry-pi-zero-2-w-2/ https://www.raspberrypi.com/news/new-raspberry-pi-zero-2-w-2... "Never one to pass up an opportunity for artistic expression, Simon even managed to squeeze a very low-resolution Raspberry Pi logo into the package ball-out, as you can see from this package and X-ray image."

190 points by geerlingguy 5y ago

rwmj 5y ago

What is the silicon spacer used for? And where is it located - there's not a picture of the three pieces of silicon in the package. Also fun to see this next to the 8086 die shots. How things have progressed in 40 years.

mkoc 5y ago
have a look here [0], Fig 1; the spacer serves really as a mechanical spacer (if dies are same or similar size); also nice for heat spreading. [0] https://www.semanticscholar.org/paper/Productivity-improvement-of-stack-package-line-die-Jin-Li/bd8bc2ea571d8e898ce74aa1d107d20fd035dbff https://www.semanticscholar.org/paper/Productivity-improveme...
magicalhippo 5y ago
You can see an illustration of the RP3A0 system-in-package in the official blog post[1]. From what I can gather[2] the spacer is actually an interposer, which for all intents and purposes functions as a PCB between the two chips, allowing for signals to be routed between the chips. Think of it as two IC's on either side of a PCB with vias connecting them. No expert though so maybe I'm mistaken. [1]: https://www.raspberrypi.com/news/new-raspberry-pi-zero-2-w-2/ https://www.raspberrypi.com/news/new-raspberry-pi-zero-2-w-2... [2]: https://sst.semiconductor-digest.com/2011/06/silicon-interposers-building-blocks-for-3d-ics/ https://sst.semiconductor-digest.com/2011/06/silicon-interpo... (section "Alternative 3D technology")
- deleted 5y ago
  [deleted]
- magicalhippo 5y ago
  I was assuming they called it an interposer for a reason. However as the sibling comment by mkoc mentions it might just be a spacer, and the X-ray image[1] of the package seems to confirm that. [1]: https://www.jeffgeerling.com/blog/2021/look-inside-raspberry-pi-zero-2-w-and-rp3a0-au https://www.jeffgeerling.com/blog/2021/look-inside-raspberry...

bigbaguette 5y ago

Between the pictures of the 8086 from 40 years ago and this, it makes me wonder what die shots will look like in 2060. Will we be slicing compute cubes?

vbezhenar 5y ago
We're using 2D schemes because we live in 3D world and we can move heat into third dimension. With 3D circuit you won't be able to transfer heat from the insides. I guess it could be possible with some integrated cooling nano pipes, but it's hard to imagine how that would work.
- FrostKiwi 5y ago
  Many pieces of circuitry on different scales are already 3D. On the big side, PCBs are printed in multiple layers, going smaller we have 3D NAND flash, micro processors are very much printed in "layers" with components being connected "one story up" and those layers are again connected "two stories above". Finally you might argue on the atomic scale, individual transistors are very much 3D as well, with how source, gate and drain are constructed. But I get your point, you can't just stack those layers ad infinitum.
  - deleted 5y ago
    [deleted]
- Causality1 5y ago
  Always been fascinating to me that we only bolt a heat sink onto one side of the board. Nobody's come up with a circuit board material that's electrically insulating but thermally conductive so we could sink an appreciable amount of heat out of the back side?
  - CamperBob2 5y ago
    Interestingly, thermal and electrical conductivity is highly correlated. You don't see a lot of materials that conduct heat well but behave as good electrical insulators, or vice versa. Both mechanisms benefit strongly from the availability of highly-mobile electrons, which is another way of saying "metal."

blamazon 5y ago

> When one codes on a Raspberry Pi one generally thinks of these CPUs as the core of the device with all the peripherals surrounding them... however the provenance of this chip is much more interesting and the CPUs are actually an afterthought. > The primary design goal of this chip was for cable TV set top boxes. For that the designers focused on transporting video. The real core of this chip is the "Video Core IV".... it's the actual master.

geerlingguy 5y ago
And fun fact: when the Pi boots up (all generations so far), the primary bootloader is the VPU (VideoCore), which then initializes the CPU and RAM. These things are slightly weird in that way.
- riobard 5y ago
  What does the VPU do after boot if the unit is headless?
  - deleted 5y ago
    [deleted]
  - sydney6 5y ago
    E.g. accelerating video decoding/encoding, OpenGL applications, etc..
  - magicalhippo 5y ago
    Well you could use it for GPGPU[1], for example[2]. [1]: https://www.cnx-software.com/2019/10/10/py-videocore6-raspberry-pi-4-gpgpu-python-library-videocore-6-gpu/ https://www.cnx-software.com/2019/10/10/py-videocore6-raspbe... [2]: https://github.com/Idein/py-videocore6/blob/master/examples/sgemm.py https://github.com/Idein/py-videocore6/blob/master/examples/...

syntaxing 5y ago

It never ceases to amaze me that someone can look at these die pictures and knows what’s going on. All I see is a bunch of copper colored squares

60Vhipx7b4JL 5y ago
after some time it's fairly easy. E.g. if you know it has a 4 core cpu, you're just looking for the same area four times.
MisterTea 5y ago
Its not far off from looking at a circuit board and recognizing layout patterns and chip shapes to get a feel for whats going on. e.g. Larger chips are usually of interest. A larger chip with one or more little rectangular chips next to or surrounding it is likely the CPU and RAM/Flash/ROM. Smaller chips are interface or power regulators depending on their proximity to ports and other components. Groups of inductors, capacitors and transistors are likely power supplies. It all comes with experience.
hobs 5y ago
I honestly thought being able to recognize ground up spices by eye was an amazing feat until I started cooking more than once a month.
stavros 5y ago
You develop your intuition by looking at (or designing) a lot of these. It's like any other profession, I guess, experience makes pattern matching easier.

skywal_l 5y ago

> It might grate on some hobbyists who see this secretive approach as the antithesis of open-source but Google Broadcom's stock price and one can see it's been a fabulously successful company. I am really interested to see what the people on HN will make of this statement.

LeifCarrotson 5y ago
I think the two factors being compared - open vs. proprietary, poor vs. wealthy - are orthogonal to each other. Does the author imply that open-source advocates believe that secrecy is bad for profits and that open-source is a way to get rich? I've not personally heard that. I do recall arguments that opening your source code will not lead to financial ruin, but that still leaves open the possibility that they're uncorrelated or only weakly correlated.
- salawat 5y ago
  Broadcom, as I understand, is as secretive as they are as a defense against patent trolling. When you have NPE's gobbling up garbage patents to sue everyone and their brother with, locking up the IP tightly is one adaptation to defend against that sort of thing. Still pisses me off to the ends of the earth.
Buttsite 5y ago
He sounds like a total moron because the next paragraph talks about how that secrecy lead to this chip being used for cable sets instead of computers until the Raspberry Pi. But pushing back the state of the art must be worth it for the stock price!
- geerlingguy 5y ago
  I think the main reason nobody else picked up these chips was because they're not really made for general purpose computing. Rather, many of the Pi engineers come from Broadcom, so it was probably more familiarity, price, and partnership that were the main drivers for it getting popular on the Pi.
5y ago

admin786 5y ago

Thanks for visiting

Namidairo 5y ago

> The only downside is that external light can actually affect the chip operation (light hitting the die releases electrons at PN junctions creating errors in circuit operation ) .. .however here the Faraday metal shield helps prevent this. Brings me back to when it was discovered that high intensity flashes could make a Raspberry Pi 2 reboot...[1] [1] https://www.raspberrypi.com/news/xenon-death-flash-a-free-physics-lesson/ https://www.raspberrypi.com/news/xenon-death-flash-a-free-ph...

squarefoot 5y ago
Many PN junction based components such as diodes and transistors are photosensitive; I recall after reading this as a kid on an old electronics magazine, I took a 2N3055, a pretty common power bipolar transistor back then, uncapped it to expose the die then connected it to my analog tester and saw it generating current when exposed to a lamp. The effect is common also in devices one could never suspect to be sensitive to light such as LEDs. They can produce light but also detect it. A few years ago someone published a project online of a MCU based keyboard (actually a button board) made of PWM driven LEDs that can both produce light and during their off cycle detect it, so that one turns them on and off just by touching them with a finger screening them from surrounding light. I attempted to search for that project without luck.
- daniel_reetz 5y ago
  I remember that project too. Might have been Paul Dietz at MERL.If you're curious, look up Paul Dietz "low cost bidirectional sensing using LEDs" and Forrest Mimms "LED Sun photometry".
  - jacquesm 5y ago
    > Forrest Mimms There's a name I haven't seen in a long time. Source of endless insight into electronics parts and schematics.
    - avhon1 5y ago

pixelpoet 5y ago

> Taking the die off the board and flipping it over reveals the typical beauty of an RF design. Knowing basically nothing about electrical engineering, what does this refer to?

moffkalast 5y ago
RF would stand for radio frequency I guess, so I suppose it's the wifi module or something.
geerlingguy 5y ago
Not an RF engineer, nor even electrical engineer, but from what little I know, if you think computer networking is voodoo magic (as I do), RF design (especially in tiny couple-mm-square chips) is like black arts mixed with ancient mythology. RF does weird things, and controlling it so it can be useful for high speed networking in the wacky environments where we put computers is IMO a pretty big feat of modern engineering. But the chip design is just pretty in its own right, with the layers coming through.
- pixelpoet 5y ago
  Thanks for the explanation, and love your videos BTW!
GeorgeTirebiter 5y ago
RF usually has not too many transistors, but sometimes a lot of coils and capacitors. You can see the coils in the design, somewhat snake-like. Capacitors can be realized in many ways, conducting material over a dielectric. Bulk capacitors are external (as you can see). Matching LC are external because those depend on the antenna; I'm a little disappointed there wasn't more detail given of the antenna, because this type I believe is a 'first' for the RPi 'in-board' antennas, in that they have two lines of series-connected capacitors inside the 'triangle'. I don't yet know how this works. RF ICs are usually hand-routed, too. So you get to see some real 'Art'.
- pixelpoet 5y ago

anonymousiam 5y ago

Nice photos! Off topic, but has anyone else noticed the scarce availability of the "regular" Raspberry Pis? A few can still be purchased at a premium price, but many vendors have no stock. Some vendors (such as Element 14) claim a backlog until 12/2022!

teh_klev 5y ago
The PiHut (UK) seem to have a pretty good stock of Pi 4 Model B's, though admittedly just the 4GB and 8GB variants: https://thepihut.com/products/raspberry-pi-4-model-b https://thepihut.com/products/raspberry-pi-4-model-b I picked one up just recently from them with no delays.
tmaly 5y ago
I just tried looking for the zero 2 W. All the sellers on the main raspberry pi site are completely sold out till next year. I managed to score the last 2 on digikey.
bliteben 5y ago
I got a 4gb recently from vilros with no real delays.
- anonymousiam 5y ago
  Well, I searched OctoPart last week and found only a few vendors with stock, and all of those were for the "kit", which includes some useful accessories that I don't need, and raises the price by about $25. Also, all of the Pi4b stock was for the 4GB version. No 8GB Pi4bs anywhere on OctoPart. So last week I ordered two Pi4b 4GB kits from Allied for $90.61 each. The last Pi4b (8GB) I bought was $75 from Newark/Element 14 in January. Amazon is now selling the 8GB Pi4b for $160.
aVx1uyD5pYWW 5y ago
https://www.raspberrypi.com/news/supply-chain-shortages-and-our-first-ever-price-increase/ https://www.raspberrypi.com/news/supply-chain-shortages-and-...

echoradio 5y ago

Am I seeing this right, that the contacts underneath the plastic housing for the chip are patterned like the Raspberry Pi logo?

georgemcbay 5y ago
Yes. It is intentional. They mentioned this in the product announcement: https://www.raspberrypi.com/news/new-raspberry-pi-zero-2-w-2/ https://www.raspberrypi.com/news/new-raspberry-pi-zero-2-w-2... "Never one to pass up an opportunity for artistic expression, Simon even managed to squeeze a very low-resolution Raspberry Pi logo into the package ball-out, as you can see from this package and X-ray image."