X-rays reveal Raspberry Pi 5's hidden secrets

I x-rayed my computer and there's so much going on in here I'm going to show you everything I learned in this video I worked with a company that specializes in imaging electronics and they use machines that are a lot like the ones at a hospital except instead of showing my bone density is reduced thanks Crohn's it shows us The Secret World inside all the parts of this tiny computer and you might have seen Jerry rig everything in D Brand's new x-ray skins it's the same process now before we dive into the pi 5's medical evaluation I have to get one thing out of the way I'm no electrical engineer I'm going to say a few things that are probably completely wrong so please feel free to correct me down in the comments I just love the fact that we have the technology to look inside these tiny devices that run so much of the world around us there's always something new to learn like I saw for the first time just how 3D the pie is I mean when you hold it and look at it it looks pretty flat but there are six layers on the screen PCB then there are more layers inside most of the chips and all all these things are put together with tiny wires just the fraction of the size of your hair but how does a little voltage come in over here to the USBC Port go through the processor that's this giant blob of circles here then get routed all around the board to ultimately shoot some bits and bites out all the io ports well let's start in the middle but before that this video isn't sponsored but if you want to help make it so I can keep doing this kind of thing go by this X-ray on a t-shirt over on Redshirt jef.com and while you're at it Go click subscribe diving right into the heart of the P this is a top- down shot of the broadcom BCM 2712 system on a chip the S so this chip packs billions of transistors inside a very tiny die area it's so small there's no way my x-rays could even begin to show it but what you can see inside this giant grid of dots is where the actual die is if I switch to a 45° angle it's actually a bit easier to see see all these tiny dots in the middle that's where the package is inside the larger 2712 chip and the these giant black dotts are the solder balls that Bond it to the Pi's PCB each of those tiny dots in the middle has a bonding wire going out to the substrate the PCB that holds the 2712 together and the grayish color over here is the metal lid or heat spreader that covers everything up and makes it look pretty there's also a ton of little Hollow circles everywhere and those are Vias or holes that go through pcbs there are even tiny Vias you can see that are probably part of the package PCB but those are so small I'd love to rip apart of M 272 someday and get more on the internals but I counted up all the balls so you don't have to the chip has a 25x 25 grid but subtracting all the missing balls there are 586 pins coming off the chip that get routed all around the board that's a lot of connections then all these giant rectangles are capacitors and they're placed right off a lot of these connections to help filter out noise from the processor to all the other components and if I flip the board around and get another shot you can see four more sets of balls W grids those are under the memory or RAM and if you zoom way in on the middle of the ram chip you can even see all its tiny bonding wires like eyelashes connecting it substrate to the memory package itself here's a top down shot of that and you can see how Raspberry Pi routed all the memory channels from the 2712 down here to the memory pins up top there's a lot of lanes to connect for lpddr4x to get the memory band with the pi5 can get look at all those little whiskers it's crazy how tiny that stuff is and it's still massive on a chip scale I also noticed this really faint lattice pattern in the memory area I'm not sure if that's part of the structure of the ram itself or what but it's not anywhere else so again a chip I'd love to dive into more but before that I'm going to zoom back out and follow some of these traces over to the left the chip routes one PCI Express Lane out to the external pcie connector that's this guy over here let's follow that and see how we can get that high-speed connector wired up this is that connector these black lines are the pins inside and it's it's a little hard to make out because of the micro SD card slot that's hanging out underneath and if you're wondering about the funky coily things at the bottom don't worry we'll get to those later but looking closely at the traces on the board a few of them even have these back and forth squiggling board designers do that when they have to deal with differential pairs that's like two wires that are sending the same signal and comparing them so for a buy one lane like you have here you actually have four wires or two pairs of wires for sending and receiving data and each wire needs an a DC coupling capacitor to remove the DC bias or offset on the line and I'm not even going to begin to say I know how all that works but if you look around on a board with PCI Express you'll likely see little pairs of tiny capacitors like these to help filter the data and the squiggles help make sure each wire or Trace is exactly the same length but even these squiggles can cause problems of their own depending on how fast the data is going so that's probably part of the reason why the pi5 is only guaranteed for PCI Gen 2 but that's only only a theory a PCI Express Theory anyway moving on to the other side of the processor what do you see here A bunch of little sets of capacitors they look like little cars driving along a super highway from the processor up to the rp1 Chip And I know from the specs the rp1 uses four PCI Express Lanes to handle USB Ethernet gpio and camera and display ports so there should be eight differential pairs are there well let's count 1 2 3 4 5 6 7 and eight all right there and just those eight wires can carry 20 Gat transfers per second of data between the rp1 and the main chip that's a lot of bandwidth so if we pop over to a top down view of rp1 and I zoom way in you can actually see the little bonding wires all around the central portion of the chip so just like the 201712 this chip is like a fourth of the size of the actual rp1 package and it could be even smaller but they made it a bigger chip so things wouldn't just short out from you touching some gopo pins at a 45° angle it's a bit of a mess but we can count this thing is laid out in an 18x18 Square pattern and there are 265 pins total going out to all the interfaces and back to the processor tilting the board just a bit more and you can really see how a modern PCB like the pi is actually like multi-layer highways with different levels of the board having all these different traces going to and fro it's kind of crazy and it's also funny how you can see how the solder on some of the taller components kind of Mounds up on the sides to get a good connection and look down here at these funny little insect leg things those are these tiny little black circuits under what I think is the fan controller but I could be mistaken and for size reference this giant crater here is one of the 2.5 mm screw holes this stuff is Tiny But popping back over to the other side of the board again this is what's inside the metal shield that covers up the Wi-Fi and Bluetooth chip another Ball g array where the actual chip is and then there's tons of circuits for RF filtering and shielding this last circuit over here heads out to the PCB antenna Trace and the circuit board gets a little weird over here this triangular thing is a cutout from the ground plane which is just a big slab of flat copper on an inner layer of the board and you can even see that with your naked eye just hold up the pie to a light where the Copper's cut out more light comes through but that along with this tiny Trace with a couple capacitors seems to make a decent little antenna built right into the pi on a lot of P clones they come with a tiny UFL connector and an external antenna but that's a little clunky so Raspberry Pi devot sweats actually a lot of board space just to avoid the external antenna and I asked the pi Engineers about this there's this extra little cut out here and that's actually used for testing an Intrepid hacker could Bridge the two dots here cut the antenna Trace here and then put their own little connector on the space but doing that would technically be illegal or at least if you did that you'd have to get your custom Raspberry Pi recertified by the FCC or whatever radio frequency body governs your part of the world but in fact some hackers have done just that on devices like the pi 02w creating their own antenna connection for a better wi-fi signal but I wouldn't recommend it the Wi-Fi and Bluetooth chip is actually identical to the one in the pi 4 but that connection is now faster on the new CPU but one area of the board that's changed radically is the bottom left corner where there's a new bolor led a new power button and a whole new USBC power delivery circuit in the center of this area is the new power IC Raspberry Pi co-designed with renesis and all around it are the power stages where it looks like there are either inductors and smaller Capac or just all capacitors now remember I'm not an electrical engineer so anything I say about the power delivery might be completely off but it looks like they use all these circuits to make it so the S so and all the other power hungry parts of the board can switch on and off and raise and lower their power quickly all while the power supply is constant and inside this chip there's another internal grid of solder points the circuit inside has all the power control and Logic for booting the p and the built-in RTC and Watchdog circuits again here's a 40 5° angle things look a little Messier in here but you can make out the USBC connector a little more clearly and it does look like all those giant circuits with the loops of wire are just inductors inductors convert energy into magnetic fields and then when energy stops going in they can release that magnetic energy as electricity again capacitors store up electrical energy then let it go I think this power supply kind of uses them in tandem to make sure the power going out to everything is stable and doesn't drop too low especially when you're doing a ton of work but again I think this power supply stuff is on the same level of magic as RF and I'm no engineer moving over a little bit you can see these funky micro HDMI connectors and then back behind there's that 2712 chip again actually from this angle you can see the top lid that heat spreader then just under that the package where there are a bunch of tiny wires bridging it to the substrate then Underneath It All the ball grid array soldering the whole thing to the pie board anyway it's like a jungle over here so let's keep moving over to the right and here's that second HDMI connector again from the top and next to it there are two combo camera display connectors it looks like the rp1 uses multiple layers on the PCB to Route signals to and from them they certainly use a lot of bandwidth and next to them there's an oscillator in the ethernet Nick which is again just next to the ethernet port and see all those little squiggles in the back of the ethernet Jack we'll get to those in a minute since the PCB is a little less crowded up here in iand let's take another look at the side profile you can see the USB ports here with the ethernet port way in the background and yes there are all those little squiggles we'll get to those soon but inside here if we move the X-ray scanner right up parallel to the board you can see how the PCB isn't just like a sheet of paper there are six layers on the pi PCB and that's actually pretty average for a modern PCB each layer has either ground planes or signal traces and between them all there are Vias that cut through to different levels so it's like an information super highway but like six of them all stacked on top of each other sometimes interfering designing these things is not easy not when you have all the that functionality crammed into something the size of a credit card so credit due to James and all the engineers who helped him lay out this board but now let's get back over to ethernet this port's really strange because if you ever look at an ethernet cable you know there's just eight wires in it logically you'd think it would just have those eight wires routed right into the PCB and the network chip would handle all the signals but ethernet's a tricky Beast unlike USB or other local interfaces ethernet could have cables hundreds of meters long and ethernet can also carry power for power over ethernet those two things plus the fact that a lot of the time you'll have your Pi plugged into one circuit and your ethernet switch or router in another means ethernet has to deal with some nasty electrical problems there could be induced power in the long cable from RF or other noise there could be a mismatch between the power levels on your switch or router and on the pi and if you want power over ethernet you need a way to separate out the DC voltage being sent into the pi and these little Tangles of wire help with all that they're called magnetics and they're basically four little isolation Transformers just chilling in the back of the port you can actually get ports without them too like on the pi 400 it Jack doesn't have them at all it has an external circuit on the board for the isolation you can do that when you have a lot of board space like the 400 does but on the pi5 there's not much so they use this integrated port and it's funny Raspberry Pi actually had to deal with the wrong ports being used once way back before they shipped the first raspberry pies in 2012 they had to hand desolder all the first batch of pies and replace all the ports because somehow they wound up with plane ports instead of the magnetics I'll leave it up to you if you want to learn more about magnetics this Digi key article has a pretty good overview but I wanted to see on another board one of the light potato boards I got from Mr Beast set does it have magnetics inside yeah well they look like they're encased on some sort of epoxy but there they are cool so that's one big reason why even with all the static electricity and signaling problems we had for the buttons the ethernet connections to all 100 boards on Mr B's set we rock solid it's always fascinating what you can learn when you see things in a different way in this case just taking a peek at the humble Raspberry Pi albeit with a half million doll Metrology machine from Nikon exposes some fascinating insights into how computers work and if you want to show off what you learned today some of the hidden secrets of the pi5 check out my x-ray shirts just in time for Christmas links below and until next time I'm Jeff Kling

Channel: Jeff Geerling

Views: 212,013

Keywords: xray, raspberry pi, pi 5, metrology, nikon, scan, ct, electronics, see, inside, visible, invisible, x-ray, ray, scanner, skin, shirt, jeff, geerling, lab, inspection, optical, aoi, quality, assurance, electric, labs, testing, underneath, pcb, bga, magnetics, transformer, isolation, ethernet, wifi, antenna, printed, circuit, board, layers, depth, usb-c, power, connector, metal, plastic, see-through

Id: MoTSSTfPXEA

Length: 13min 25sec (805 seconds)

Published: Thu Dec 07 2023