[HN Gopher] Raspberry Pi Zero 2 W die shots
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Raspberry Pi Zero 2 W die shots
Author : geerlingguy
Score : 175 points
Date : 2021-11-08 13:27 UTC (9 hours ago)
(HTM) web link (electronupdate.blogspot.com)
(TXT) w3m dump (electronupdate.blogspot.com)
| anonymousiam wrote:
| 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!
| bliteben wrote:
| I got a 4gb recently from vilros with no real delays.
| teh_klev wrote:
| 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
|
| I picked one up just recently from them with no delays.
| aVx1uyD5pYWW wrote:
| https://www.raspberrypi.com/news/supply-chain-shortages-and-...
| syntaxing wrote:
| 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
| MisterTea wrote:
| 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 wrote:
| 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.
| 60Vhipx7b4JL wrote:
| 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.
| stavros wrote:
| 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.
| rwmj wrote:
| 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.
| magicalhippo wrote:
| 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...
|
| [2]: https://sst.semiconductor-digest.com/2011/06/silicon-
| interpo... (section "Alternative 3D technology")
| magicalhippo wrote:
| 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...
| [deleted]
| mkoc wrote:
| 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-
| improveme...
| blamazon wrote:
| > 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 wrote:
| 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 wrote:
| What does the VPU do after boot if the unit is headless?
| [deleted]
| sydney6 wrote:
| E.g. accelerating video decoding/encoding, OpenGL
| applications, etc..
| magicalhippo wrote:
| Well you could use it for GPGPU[1], for example[2].
|
| [1]: https://www.cnx-software.com/2019/10/10/py-
| videocore6-raspbe...
|
| [2]: https://github.com/Idein/py-
| videocore6/blob/master/examples/...
| admin786 wrote:
| Thanks for visiting
| skywal_l wrote:
| > 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 wrote:
| 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 wrote:
| 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.
| moffkalast wrote:
| > Company keeping market leading advances secret brings in
| loads of money. More at 11.
|
| I'm sure exactly nobody is surprised. Open source is the
| antithesis of profitability, as such not being open source
| equals vast amounts of money, on average.
| Buttsite wrote:
| 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 wrote:
| 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.
| megous wrote:
| I certainly don't understand why so many jumped on a bandwagon
| of a SBC which was basically an obscure GPU with some
| accidentally attached ARM cores, on an I/O starved SoC design,
| that still doesn't have a useful opensource bootloader even
| after 8 years or so,... when much more interesting, more open,
| and chepaer alternatives started appearing rather quickly after
| the first Rpis.
| justin66 wrote:
| If you're actually interested in figuring this out for
| yourself instead of attributing it to "marketing," compare
| and contrast with the situation of the Beaglebone boards.
| Those came out several years prior to the Raspberry Pi, get
| plenty of PR and press, have received really good updates
| through the years, have the direct backing of a major
| manufacturer, are very open, and have a more conventional SoC
| design. In short, we're talking about stuff that failed to
| hold back the Raspberry Pi onslaught even though it existed
| years before the Pi and even though it addresses the stuff
| you said you care about.
|
| Basically, Pi users want different things than you want, and
| the Pi people were pretty good at delivering those things. I
| assume the attention to early education in addition to
| hackers and makers, and somehow persuading or inspiring some
| hackers to work on a Debian armhf port with user-friendly
| features at a time when most people already wanted armhf to
| just go away and die, were decisive. Those were what really
| set the Pi apart and served to bring in more and more
| developers and users. After that's it's a virtuous cycle of
| more and more content creation and enthusiasm surrounding the
| platform.
| foxfluff wrote:
| Anecdotally, Beagle had zero marketing compared to the Pi.
| Only hardcore geeks had heard of it, whereas when the Pi
| came out, "normies" wowed at this "cheap credit card sized
| computer!" that they saw on the news. In schools and
| workplaces, you could find plenty of people who had heard
| of the Pi or even had bought one, but they'd never heard of
| the alternatives. Plenty of people literally think the Pi
| was the first SBC too. And Pi quickly ended up on the
| virtual shelves of mainstream electronics stores (along
| with the Arduinos); the alternatives never came (the only
| one I remember seeing is the Asus Tinkerboard which I guess
| has all the marketing power of Asus behind it so that's not
| too unexpected), and you still have to shop for them on
| Ebay/Ali*/whatever.
| justin66 wrote:
| > Anecdotally, Beagle had zero marketing compared to the
| Pi. Only hardcore geeks had heard of it, whereas when the
| Pi came out, "normies" wowed at this "cheap credit card
| sized computer!" that they saw on the news.
|
| I remember those times, and I'm not sure how to quantify
| this stuff, and it's not like I know about marketing in
| general. But...
|
| I'm not sure the Pi had _more_ marketing. I 'm very sure
| it had _more effective_ marketing. It seems to me like
| there are probably some lessons there if somebody wanted
| to dig into it. I mean honestly, the Pi guys were like a
| handful of Cambridge people with no money and an in with
| Broadcom in the beginning. I 'm pretty sure I found out
| about the Beagle from none other than _Texas
| Instruments._
|
| It seems to me like the one-offs, clones, and general
| other stuff that came after Pi and Beagle are
| deliberately targeting the Beagle-type people rather than
| the Pi-type people, and there are just fewer of those
| people. All the industrial sales of Pi hardware suggest
| that once you've grown the user base beyond a certain
| point, you can target the Pi-type people all day long and
| the hackers and industrial customers will hop on board
| because they value the volume of what you're producing.
| bigiain wrote:
| $35
|
| (At least that was the "Holy fuck, really? I gonna get one of
| those" thing for me.)
| sneak wrote:
| > _when much more interesting, more open, and chepaer
| alternatives started appearing rather quickly after the first
| Rpis_
|
| Like what?
| ArgyleSound wrote:
| Which ones? I'm only aware of boards that aren't anywhere
| near the PS5-35 price class the Raspberry Pis inhabit, and
| even then there's just absolutely nothing like the third
| party ecosystem that the Pis have.
| cillian64 wrote:
| Because I can google "How to drive addressable LEDs from
| Raspberry Pi", for example, and find a lot of example
| projects and blog posts and not have to reinvent the wheel.
| It's inelegant for sure, but great for prototyping or duct
| tape projects where you want to stand on the shoulders of
| others and just get something working quickly.
| megous wrote:
| You can google the exact same phrase and just use the Rpi
| solution/code on any other Linux based SBC, because gpio
| has a standard userspace API on Linux. All you change is
| pin mapping at most.
|
| Though yeah, if you don't care about the SBC capabilities
| at all, and your goal is to just drive some LEDs from
| Linux, you can just as well buy whatever is familiar to
| you, regardless of any shortcomings.
| monocasa wrote:
| The addressable LEDs aren't typically just bit banging
| GPIOs. There's no clock line with common protocols in the
| space like the WS2812, and they're very susceptible to
| jitter. Twiddling GPIOs from user space is basically a
| non starter.
|
| I've had success though with using the MOSI line from a
| SPI master and carefully crafting the bit pattern and
| timing to get the waveform I want. It takes some manual
| work though, more than what you get from user space.
| geerlingguy wrote:
| IMO, it comes down to the support and ecosystem. Even though
| it would be nice to have something more open than Broadcom's
| chips, the corporate/foundation backing of the project, and
| the broad adoption after those first few revisions (coupled
| with the fact that Pis are still some of the cheapest options
| around) means that someone can come into the ecosystem blind
| and not have to spend hours or days just figuring out how to
| get an OS running on the darn thing.
|
| And then the fact that you can still run a supported modern
| OS on an almost 10 year old board... that doesn't seem to
| happen with other SBCs (most are basically shelved after a
| couple years), and you end up running ancient OSes on them or
| obscure community-driven OSes that break in a hundred
| different ways.
| megous wrote:
| There are a lot of boards that have mainline u-boot/Linux
| support, don't need neither any wonky 4MiB binary firmware
| which does who knows what, nor any vendor specific tools to
| control basic things like HDMI, or CPU frequency, and just
| work for years with any arm based distro.
|
| Personally I think it's just a better marketing.
| forty wrote:
| You can boot your rpi to mainline uboot (it does not
| remove the wonky firmware though :) )
|
| I feel wonky firmwares are pretty common in the arm world
| though (and in other worlds too)
| floatboth wrote:
| You don't need vendor specific tools. Especially not on
| the pi 4 but even before that. The RPi foundation stayed
| on a 32 bit distro with the proprietary graphics stack
| forever due to some silly fear of breaking.. something
| (?) or whatever but mainline linux has been able to
| manage everything about graphics and display with the vc4
| drm/kms driver for ages. CPU frequency has _of course_
| been controlled by a mainline kernel driver for ages -
| heck that 's supported in all of the BSD OSes as well.
| michaelt wrote:
| That wasn't my experience, pre-raspberry-pi.
|
| There were projects, sure - but they rarely sold in large
| volumes. That meant not many paid developers. And if you
| had a problem you'd be lucky if someone online had even
| experienced the same problem, let alone found a fix for
| it.
|
| Every chip vendor seemed to have their own kernel fork
| with their own patches, and didn't much care to get them
| upstreamed. And of course, their kernel would be ancient
| - they're selling it for things like automotive
| infotainment systems which don't give a shit about
| security.
|
| Want to attach, say, a battery-backed RTC to your SBC? I
| hope you know the difference between a dtc and a dtbi.
| And even if someone else has been nice enough to get the
| same part working on their SBC, just because a TI
| processor needs the line 'dmas = < 0x21 0x1c 0x00 0x21
| 0x1d 0x00 >;' doesn't mean you can copy that to a
| Freescale processor and expect it to work.
|
| More than once I brought SBCs that came with a connector
| for a MIPI camera - but no camera available, and no
| software either. You want a camera? Plug in a USB webcam.
|
| And let's be honest: If you want features like wifi and
| hardware h264 support you're going to be dealing with
| wonky binary firmware anyway.
| pixelpoet wrote:
| > 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 wrote:
| RF would stand for radio frequency I guess, so I suppose it's
| the wifi module or something.
| GeorgeTirebiter wrote:
| 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'.
| geerlingguy wrote:
| 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.
| Namidairo wrote:
| > 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-
| ph...
| squarefoot wrote:
| 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 wrote:
| 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 wrote:
| > Forrest Mimms
|
| There's a name I haven't seen in a long time. Source of
| endless insight into electronics parts and schematics.
| avhon1 wrote:
| He did a series of columns for Make Magazine. A
| compilation book titled "Make: Forrest Mims' Science
| Experiments" was published in 2016.
|
| https://www.makershed.com/products/forrest-mims-science-
| expe...
| dangets wrote:
| A self-directed project I did for a university course was to
| make a Morse code transmitter and receiver. I was able to use
| the same LED for both.
| adolph wrote:
| By using the same LED as a receiver too?
|
| https://makezine.com/projects/how-to-use-leds-to-detect-
| ligh...
| bigbaguette wrote:
| 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 wrote:
| 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.
| Causality1 wrote:
| 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?
| moffkalast wrote:
| Yeah especially with something like the Pi, you could
| effectively double the core count by slapping another chip
| on the other side and add another heatsink.
| michaelt wrote:
| _> 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?_
|
| In applications like high-power LED lights, you'll often
| get 'Insulated Metal Substrate' PCBs where the printed
| circuit is on an aluminium or copper board, separated by a
| very thin electrically insulating layer. [1]
|
| However, this has a few downsides: The electrically
| insulating layers aren't perfectly thermally conductive,
| meaning a directly attached heatsink will usually perform
| better; if you make a complex board with 8+ layers of
| copper (like a modern motherboard) you end up with 8+
| layers of insulation; and it's nigh-impossible to use
| through-hole components.
|
| For LED lighting those are non-issues and, a top-mounted
| heatsink wasn't an option anyway.
|
| [1] https://dm.henkel-
| dam.com/is/content/henkel/Bergquist%20Comp...
| CamperBob2 wrote:
| 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."
| [deleted]
| nanomonkey wrote:
| There are in fact thermal PCBs (a.k.a. MCPCB) used for LEDs
| and other electronics that need to dissipate heat. They
| have an aluminum or copper layer that supplies rigidity and
| a heat path out the backside or center of a PCB.
| StillBored wrote:
| I put a fairly large/flat heatsink on the back metal of the
| heatsink support bracket on my intel (overclocked) desktop
| a few years back it pulled the temps down a couple degrees
| when a fan was blowing at it under moderate load.
|
| I've been thinking about this for my ryzen lately too,
| since it appears keeping the top of the die cool is
| unusually challenging. A lot of mobile/etc parts use the
| PCB ground plane as a heatsink, so it makes sense that if
| you can attach a larger heatsink to the back of a normal PC
| board you should be able to pull heat out of both sides.
| Particularly in a water cooled system where the top of the
| heat spreader is remaining fairly cool but the surrounding
| board is heating up (like my ryzen).
| kortex wrote:
| Oh, that is in fact an important heat path on all but the
| most intensive components. But with high power components,
| the heat flux is pretty insane. You can move a huge amount
| of heat with heat pipes, and it's just easier to move heat
| out the back.
| FrostKiwi wrote:
| 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]
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