The Anatomy of a Motherboard
The motherboard is often forgotten as a high tech bit of kit in most gaming PCs – it’s the slab of fibreglass that everything plugs into, right? Well yes, but it’s jam-packed with amazing tech, so in this video I want to walk you through the anatomy of a modern motherboard and hopefully you’ll leave here with a load of knowledge and a new-found appreciation for this impressive part of your system.
Actually, let’s start with the PCB, or printed circuit board, itself. That isn’t exactly simple, for starters these days anything with PCIe Gen 4 or 5 are between 6 and 10 layer PCBs – as in there are 10 layers of copper traces running through here. Yeah, that’s insane! That’s in part thanks to the sheer complexity of these boards – this X670 board has FOUR M.2 slots, an x16 and two x4 PCIe slots, I/O out the wazoo, and something like 20 power phases in the VRM. That’s a lot of connections to make, hence the need for so many layers. It’s also needed for signal integrity. If you had two of those M.2 slot’s lanes run directly on top of eachother just one layer apart, you’d get crosstalk between the two lines corrupting data and slowing things down drastically, so they are kept further apart.
The next obvious point is the CPU socket – especially since now both Intel and AMD are using the LGA or land grid array style socket. AMD have stuck with their naming scheme though, whereas Intel generally just call it LGA and the number of pins – so LGA1700 is the current setup. AMD’s AM5 socket actually has just 18 more pins for a total of 1718, although one key difference is the style. Intel ops to have a lot of their capacitors in the centre of the socket and on the back of the chip, whereas AMD has them on the back of the board and on the top of the CPU, so AMD has basically a flat grid of pins, whereas Intel spreads them out more in a hollow rectangle.
The part of the board that powers the CPU is the VRMs or voltage regulator module, which is what takes the 12V from the power supply and drops it down to the 1.2V or so the CPU actually needs. The first part of the chain is the controller. On this board that’s an ASP2100R, a Pulse Width Modulation (PWM) controller that activates the 13 total phases – likely 6 pairs of teamed phases and an extra for the RAM or chipset. Each phase is made up of two MOSFETs – basically like digital switches – a diode, inductor and capacitor. The MOSFETs switch on and off tens of thousands of times per second to regulate the voltage down to the right level. The more phases you have, the more power and stability you generally get, and the reason for teaming phases together is the ASP2100R controller likely only has 8 channels available, so you just run two pairs of phases from one control signal.
When it comes to the RAM, if you are running DDR5, the modules themselves have the power circuitry onboard, so generally you don’t need any power phases for the RAM, although with DDR4 you certainly do. Otherwise, the main thing with RAM is the track length. Each of the tracks need to be the same length so data arrives at the same time – at 5600MT/s that’d be just 0.17ns. 0.2 of A NANOSECOND. That’s how fast each new 64 bit byte is coming in. You can see the rather squiggly lines especially from the central traces as they try to match the length of the outer pins.
One of the most obvious parts of the motherboard is the chipset. These days, this is somewhat of a glorified PCIe hub for all the connected devices – although AMD thinks it’s of so much use that for their X670 boards, they’ve put TWO chipset dies daisy-chained together for as much connectivity as possible. They often connect to things like the extra M.2 slots, USB controllers, audio codec, LAN and WiFi, the x4 and x1 PCIe slots, and the SATA ports. For Intel boards you’ll find a single PCH, or Platform Controller Hub, which again connects to the CPU via basically PCIe and allows things like M.2s, SATA ports and I/O to connect in.
Often chipsets can contain USB controllers natively, but more often than not a motherboard will have an additional USB controller to handle some of the many USB ports often included on modern boards. On this B760 board, that’s this guy here, an ASMEDIA ASM1074, a USB 3.2 Gen1 hub and controller, which runs up to four USB ports on the board. In this case you can see the traces headed to the USB 3 and Type C front panel header connectors, so this is the controller your front panel USB ports will use. You’ll also find hub chips too, which aren’t full controllers, just a way to connect multiple ports to one port on a controller. On this board that’s this Realtek chip. Sometimes a signal isn’t quite strong enough to reach where it needs to go for sure, so it needs a redriver chip. This board has a USB redriver in the form of a Genesys Logic GL9901 – and to round off the USB chips, since this board has a Type C port that supports some amount of power delivery, there is also a USB C PD chip from Realtek here too.
Something you’ll also find near the rear I/O is the LAN controller. In this case that’s a Realtek 2.5Gb ethernet controller which is incredibly common now. Intel pretty much mandantes 2.5G ethernet now, and it looks like AMD might do too. These controllers are cheap enough that motherboard vendors are using them instead of gigabit controllers – which I’m pretty happy to see. WiFi is almost always done by an external module – either an M.2 E key slot or vertical mount like this one.
You might be interested in the audio side of things – there was a big fuss about the audio section of motherboards around Z97 or Z170. Basically as part of the whole “interference with other traces” thing, motherboard vendors started isolating the section of the board the audio codec used. You can see the traces running along the side from their hidden audio codec. I’m not 100% sure which one they are actually using here, but the classic go-to is the Realtek ALC1220. Asus have taken this isolation a step further and have soldered a cover on top to, in theory, keep any noise out of your clean audio.
If your motherboard has video outputs, you might find one of these chips too. This is an HDMI level shifter, basically the integrated GPU in your CPU produces a frame, then the level shifter bumps the signals up to be compliant with the HDMI standard, then it gets sent out via the HDMI port. This chip in particular was originally released in 2009 but has since been updated to support HDMI 1.4, full 24 bit colour and even has pins to control input jitter elimination features. Pretty cool!
On the PCIe front, especially with the introduction of PCIe Gen 5, that connection is incredibly sensitive. I mean PCIe Gen 5 is putting 32GT/s PER LANE! That’s a new packet every 31 PICOSECONDS, so understandably you need those signals to be incredibly stable. That’s why you’ll find these Phison PS7101 Gen 5 redriver chips wherever there are Gen 5 connections. That basically re-sends the signal, which will add some latency, but means the signal is as stable as possible for reliable transmission. If you need to split some lanes though, a rather common requirement on boards with far more slots than they have dedicated lanes, you might need a multiplexer. This basically acts like a two-into-one turnstyle that lets you use the same, say 4 PCIe lanes, to run both an M.2 slot and a network card, where the data takes turns using the upstream lanes. This is one of the main functions of a chipset actually!
One of the interesting things you might not have thought about is that every function on the board generally has a dedicated chip for it. Hardware monitoring is done by this big Nuvoton chip in the middle of the board – so all those temperature, current and fan RPM readings all come from this chip. The fans are run by these linear fan driver ICs, the RGB is run by dedicated chips – in this case Asus’ own AURA 32AUO chip, and of course the BIOS is stored on a flash chip like this Winbond 256Mbit chip on the X670E board.
And that is the anatomy of a motherboard. Of course there is plenty more we could talk about, but I think that’s enough information for now… If you have any questions, have anything to add or if I got anything wrong, please do let me know in the comments down below.
