You might have a desktop PC at work, schoolhouse, or home. You might use one to work out tax returns or play the latest games; y'all might even be into edifice and tweaking computers. But how well practice you know the components that make up a PC? Accept the humble motherboard -- it sits there, quietly keeping everything running, and rarely gets the same attention equally the CPU or graphics card.

Motherboards are remarkably of import though, and full of actually absurd technology. So let's go all Grayness's Anatomy, and dissect the motherboard -- breaking downward its various parts and seeing what each flake does!

A uncomplicated overview to start with...

Let u.s.a. brainstorm with the main part of a motherboard. In essence, it serves ii purposes:

  • Provide electrical power to the individual components
  • Provide a route to permit the components to communicate with each other

In that location are other things a motherboard does (e.grand. holds the components in place, or provides feedback as to how well everything is performance) but the aforementioned aspects are critical to how a PC operates, that nigh every other part that makes upward the motherboard, is related to these two things.

Most every motherboard used in a standard desktop PC today will have sockets for the central processing unit (CPU), retentivity modules (nearly ever a type of DRAM), add-in expansion cards (such a graphics card), storage, input/ouputs, and a means to communicate with other computers and systems.

Standard motherboards initially differ in terms of their size, and there are industry-wide standards that manufacturers tend to adhere to (and plenty of others that don't). The master sizes you're likely to come across are:

  • Standard ATX - 12 × 9.6 inches (305 × 244 mm)
  • Micro ATX - ix.6 × ix.6 inches (244 × 244 mm)
  • Mini ATX - 5.9 × 5.9 inches (150 × 150 mm)

Yous can see a far more comprehensive list on Wikipedia but we'll only stick to standard ATX for simplicity, because the differences generally lie in the number of sockets available to exist powered and continued; a bigger motherboard permits more than sockets.

Only what exactly is a motherboard?

A motherboard is merely a big electronic printed circuit board, with lots of connectors to plug things into and hundreds, if not thousands, of feet of electrical traces that run between the diverse sockets. Theoretically, the board isn't needed: you could connect everything together by using a huge mass of wires. The operation would be terrible, though, as the signals would interfere with i another, and there would be notable power losses by using this method, besides.

We'll begin our breakdown by using a typical ATX motherboard. The image below corresponds to an Asus Z97-Pro Gamer and its advent, features, and functions tin can be found in dozens more similar information technology.

The only problem with the picture (other than the motherboard being quite... umm... well, used) is that there are a lot of visible components, making it trickier to spot everything clearly.

Allow'south strip it all away and await at a simplified diagram to begin with (below).

That'south amend, simply there is nonetheless a lot of sockets and connectors to talk about! Let'southward start near the top, with the near important 1 of all.

Wiring up the brains of a PC

The diagram has a structure labelled LGA1150. This is the proper name used by Intel to describe the socket used to hold many of their CPUs. The messages, LGA, correspond State Grid Array, a common type of packaging technology for CPUs and other integrated circuits.

LGA systems take lots of piffling pins in the motherboard, or in a socket on the board, to provide power and communications to the processor. You tin can see them in the picture below:

The metal subclass holds the CPU in place but it's getting in the way of seeing the pins clearly, and then permit's movement information technology to one side.

Remember the name for this? LGA1150. The number is for how many pins in that location are in this socket. Nosotros'll explore the connections for a CPU in another article, but for at present nosotros'll just point out that motherboards for other CPUs will take more or fewer pins.

In full general, the more capable the CPU (in terms of number of cores, corporeality of enshroud, etc), the more pins volition be found in the socket. A large number of these connections will be used to send and receive data to the next important feature on a motherboard.

Large brains need big retentiveness

The sockets or slots that are always the closest to the CPU are those that hold DRAM modules, aka organisation retention. These are connected direct to the CPU and nothing else on the motherboard. The number of DRAM slots depend by and large on the CPU, as the controller for the retentiveness is built into the central processor.

In the case nosotros're looking at, the CPU that fits into this motherboard has 2 memory controllers, with each one treatment two sticks of memory - hence there are 4 sockets in full. You lot can see that, on this motherboard, the retention sockets are colored in way to let yous know which ones are managed by which controller. They're commonly called memory channels, so channel #1 handles ii of the slots and channel #2 handles the other two.

For this particular motherboard, the colors of the slots can be a petty confusing (and it certainly confused this author!): the two black slots are actually one each for the 2 memory controllers (and same for the grey ones). And so the blackness slot closest to the CPU socket is channel #1, and the next black one is channel #2.

It'due south colored like this to encourage you utilize the motherboard in what is called dual memory channel style - by using both controllers at the same time, the overall operation of the memory organization is increased. And then permit's say y'all had two RAM modules, each one 8 GB in size. No matter what slots yous put them in, yous'll always have a total of 16 GB of available retention.

However, if you put both modules into both of the black slots (or both of the greyness slots), the CPU will essentially have double the routes possible to access that retention. Do it the other way (one module in each color) and the system will be forced to access the memory with just the 1 memory controller. Given that it can only manage ane route at a time, information technology'south not hard to see how this doesn't assist functioning.

This CPU/motherboard combination uses DDR3 SDRAM (double information rate version iii, synchronous dynamic random access retentiveness) chips and each socket holds ane SIMM or DIMM. The 'IMM' part stands for Inline Memory Module; the S and D refers to where the module has ane side filled with chips or both sides (unmarried or dual).

Along the bottom edge of the memory module are lots of gold plated connectors, and this type of memory has 240 of them in full (120 each side). These provide the power and data signals for the chips.

A single DIMM of DDR3 SDRAM. Paradigm: Crucial

Bigger modules would permit you to take more memory, but the whole setup is express past the pins on the CPU (most half of the 1150 pins in this example are defended to handle these memory chips) and space for all of the traces or electrical wires in the motherboard.

The computer manufacture has stuck with using 240 pins on memory modules since 2004 and shows no signs of changing any fourth dimension presently. To improve memory performance, the chips merely run faster with each new version released. In the example we're looking at, the CPU's memory controllers can each send and receive 64 bits of data per clock cycle. And then with ii controllers, the memory sticks will having 128 pins dedicated to transferring information. So why 240 pins?

Each memory flake on the DIMM (sixteen in total, 8 per side) can transfer 8 bits per clock wheel. That means each scrap needs eight pins, just for information transfers; withal, ii chips share the same data pins, so simply 64 of the 240 are data ones. The remaining 176 pins are required for timing and reference purposes, transmitting the addresses of the data (location of where the data is on the module), controlling the chips, and providing electric power.

So you can see that having more than than 240 pins won't necessarily make things better!

RAM isn't the only matter that's hooked upward to the CPU

System retention is connected directly to the fundamental processor to boost operation, but there are other sockets on the motherboard that are wired a bit like this (and for the same reason). They utilize a connection applied science called PCI Express (PCIe, for short) and every modernistic CPU has a PCIe controller congenital into it.

These controllers can handle multiple connections (typically referred to every bit lanes), even though information technology is a 'point-to-indicate' system, meaning that the lanes in the socket aren't shared with any other device. In our example, the CPU's PCI Limited controller has sixteen lanes.

The image beneath shows three sockets: the meridian two are PCI Express, while the bottom one is a much older system called PCI (related to PCIe, simply a lot slower). The picayune ane at the top is labelled PCIEX1_1 because information technology is a single lane socket; the one beneath it is a 16 lane socket.

If you lot ringlet support and expect at the whole motherboard again, y'all can see that there are:

  • 2x PCI Limited 1 lane sockets
  • 3x PCI Express sixteen lane sockets
  • 2x PCI sockets

But if the CPU'south controller but has sixteen lanes, what's going on? Outset of all, merely PCIEX16_1 and PCIEX16_2 are connected to the CPU - the third one, and the ii single lane sockets are continued to another processor on the motherboard (more well-nigh that in a moment). Secondly, if both sockets were filled with devices that use 16 PCIe lanes, and then the CPU volition just dedicate 8 lanes to each.

This is the case of all CPUs today; they take a limited number of lanes, so as more devices get connected to the CPU, each i gets a smaller number of lanes to work with.

Different CPU and motherboard configurations take their own way of handling of this. For case, Gigabyte'southward B450M Gaming motherboard has i PCIe 16 lane socket, 1 PCIe 4 lane socket and a One thousand.2 socket that uses 4 PCIe lanes. With only 16 lanes available from the CPU, using any two sockets will force the larger x16 one to exist capped to 8 lanes.

So what kind of things utilize those sockets? The most common choices are:

  • 16 lanes = graphics card
  • 4 lanes = solid state drives (SSD storage)
  • 1 lane = sound cards, network adapters

Y'all can run into the difference betwixt the connectors in the image above. The graphics card sports the longer 16 lane i, compared to the sound card's little one-lane setup. The latter has far less information to transfer than the former, so it doesn't need all those actress lanes.

In our motherboard example, similar all others, has lots more sockets and connections to manage, and so the CPU gets a helping paw from some other processor.

Allow's head southward and cross the span

If we become back 15 years or so, and look at motherboards from that era, there were two additional fries built into them to support the CPU. Together, they were called a chip set (ordinarily concatenated to chipset), and individually they were called the Northbridge (NB) and Southbridge (SB) chips.

The quondam handled the system retentivity and graphics card, the latter processed the information and instructions for everything else.

The in a higher place image, of an ASRock 939SLI32 motherboard, conspicuously shows the NB/SB chips - they're both hidden under aluminum heatsinks, but the one closest to the CPU socket in the middle of the image is the Northbridge. A few years afterward this production was around, both Intel and AMD released CPUs that had the NB integrated into the primal processor.

The Southbridge, though, has remained separate and is likely to be so for the foreseeable hereafter. Interestingly, both CPU manufacturers have stopped calling it the SB and oftentimes refer to it equally the chipset (Intel's proper name for it is the PCH, platform controller hub), even though it'due south just a single scrap!

On our more modern example from Asus, the SB is besides covered with a heatsink, so permit'southward pop it off and accept a look at the actress processor.

This chip is an avant-garde controller, handling multiple types and numbers of connections. Specifically, it'southward an Intel Z97 chipset and offers the post-obit features:

  • 8 PCI Express lanes (version two.0 PCIe)
  • xiv USB ports (6 for version iii.0, 8 for version ii.0)
  • 6 Serial ATA ports (version 3.0 SATA)

Information technology also has an integrated network adapter, an integrated sound scrap, a VGA display output, and a whole host of other timing and controlling systems. Other motherboards will have more basic/avant-garde chipsets (providing more PCIe lanes, for instance) but in general, most chipsets offering the same kind of features.

For this particular motherboard, this is the processor that handles the unmarried lane PCIe slots, the third 16 lane slot, and the M.2 slot. Like many newer chipsets, it handles all of these different connections by using a ready of loftier speed ports that can be switched to PCI Express, USB, SATA, or networking, depending on what is continued at the fourth dimension. This, unfortunately, places a limit on how many devices plugged into the motherboard, despite all those sockets.

In the case of our Asus motherboard, the SATA ports (used to attach hard drives, DVD burners, etc) are grouped as shown above considering of this limitation. The block of 4 ports in the eye use the chipset'southward standard USB connections, whereas the two on the left apply some of these loftier speed connections.

So if you lot use the ones on the left, then the chipset will have fewer connections for other sockets. The same is true for the USB three.0 ports. At that place is support for upwards to 6 devices, but two of these ports will likewise swallow into the loftier speed connections.

The Thou.2 socket, used to connect SSD storage, uses the fast system, too (along with the third xvi lane PCI Express slot on this motherboard); however, on some CPU/motherboard combinations, the One thousand.2 sockets connect directly to the CPU, as many newer products accept more than than 16 PCIe lanes to distribute and use.

Forth the left manus side of our motherboard, at that place is a row of connectors generally called the I/O ready (input/output) and in this instance, the Southbridge chip (or chipset) simply handles a few of them:

  • PS/2 connector - for keyboards/mice (top left)
  • VGA connector - for older/cheaper monitors (elevation eye)
  • USB 2.0 ports - black in colour (bottom left)
  • USB three.0 ports - blue in color (lesser middle)

The CPU's integrated graphics processor handles the HDMI and DVI-D sockets (bottom middle) simply the rest are managed past additional chips. Most motherboard have a raft of extra little processors to manage all kinds of things, so let's accept a look at some of those.

Additional fries for additional help

CPUs and chipsets accept a limit to what they tin support or connect to, so most motherboard manufacturers offering products with extra features, thanks to the utilise of other integrated circuits. This might be to provide actress SATA ports, for instance, or provide connections for older devices.

The Asus motherboard we've been looking at is no different. For example, the Nuvoton NCT6791D chip handles all of the little connectors for fans and the temperature sensors built into the lath; the Asmedia ASM1083 processor adjacent to information technology manages the two legacy PCI sockets, because the Intel Z97 chip has no such adequacy.

Although Intel's chipset has a built-in network adapter, it uses some of those valuable high speed connections, so Asus added some other Intel chip (an I218V) to manage the crimson ethernet socket we saw in the I/O set. The above image does no justice to how small this chip is: it's just 0.24 inches (six mm) square!

The stadium-shaped silver metal affair is a type of quartz crystal oscillator -- it provides a low frequency timing signal, for the networking bit to stay synchronized.

Something else that this motherboard offers as an extra is a chip to handle audio. Yep, the Intel chipset has its ain integrated sound processor, just it'south been bypassed for the same kind of reasons that Asus have added a separate networking flake and that most people add a graphics card to replace the integrated graphics processor in the CPU. In other words, the extra chip is just better!

Non all of the extra chips on the motherboard are about replacing integrated ones, many are there to manage or control the operation of the board in general.

These little chips are PCI Express switches and aid the CPU and Southbridge manage the 16 lane PCIe connectors, when they demand to distribute the lanes to more devices.

Motherboards with the ability to overclock CPUs, chipsets, and system memory are now commonplace, and many come with extra integrated circuits to manage this. In our case lath, highlighted in red, Asus is using its own design called the TPU ('TurboV Processing Unit of measurement') that adjusts clock speeds and voltages to a fine level of command and aligning.

The little Pm25LD512 device next to it, highlighted in blue, is a flash memory chip that stores the clock and voltage settings when the motherboard is powered off, so you lot don't take to redo them, every time you power upward the PC.

Every single motherboard has at least one flash memory device, though, and this is for storing the motherboard's BIOS (the bones hardware initialization operating system that gets everything going before loading Windows, Linux, macOS, etc).

This Winbond fleck is just 8 MB in size but that'southward more than than enough to hold all of the software needed. This kind of flash memory is designed to use very little ability when in use and hold onto its data for decades.

When you switch on the PC, the contents of the flash memory are copied directly to the CPU's cache or system memory, and and so run from in that location, for maximum performance. However, the one thing that this memory tin can't concur onto is time.

This motherboard, similar every other one effectually, uses a CR2032 prison cell to ability a unproblematic timing excursion, that keeps track of the data and time for the motherboard. Of class, the power of a cell doesn't last forever and once information technology'southward flat, the motherboard will default to a starting fourth dimension/date in the flash retention.

And speaking of power, there are more connectors for that, too!

Bring me the power, Igor!

To provide the voltage and electric current required to run the motherboard and many of the devices attached to it, the computer's power supply unit of measurement (PSU) will have a number of standard connectors for this purpose. The master one is a 24-pivot ATX12V version 2.4 socket.

The amount of current that can be fatigued from the pins depends on the PSU, just the voltages are manufacture prepare to +three.3, +five, and +12 volts.

The bulk of the current for the CPU is fatigued off the 12 volt pins, but for modern high-finish systems, it's not enough. To get around this problem, there is an additional eight-pin power connector that provides another four set of 12V pins to be used.

The connectors from the PSU have colour coded wires to help identify what each wire is for, but the sockets on the motherboard don't tell you very much. Here's a diagram for the two ability sockets:

The +three.3V, +5, and +12V lines supply power to the various components on the motherboard itself, and also powers the CPU, DRAM, and whatsoever devices plugged into the extension sockets such equally the USB or PCI Express slots. Annihilation using the SATA ports need power directly from the PSU, though, and PCI Limited sockets can only provide up to 75W. If the device needs more juice than that -- lots of graphics cards practise -- then they'll need to be hooked up to the PSU direct, besides.

However, there'south a larger trouble than having enough 12V pins: CPUs don't run on that voltage.

For instance, the Intel CPUs designed to run on this Asus Z97 motherboard run off voltages between 0.7 and ane.4 volts. It'southward not a fixed voltage, considering today's CPUs vary how much voltage they're running on to save power and reduce heat; so when idling on the desktop, the CPU can tootle away with less than 0.8 volts. Then with all the cores fully loaded and working away, information technology rises to one.4 volts or more than.

Power supply units are designed to convert mains Ac voltage (110 or 230, depending on the state) into fixed DC voltages, so boosted circuits must be used to drib them lower and vary them every bit required. These circuits are called voltage regulation modules (VRMs, for short) and can be easily spotted on any motherboard.

Each VRM is typically comprises iv components:

  • 2x MOSFETs - high electric current switching transistors (blueish)
  • 1x inductor - besides known as a choke (purple)
  • 1x capacitor (yellowish)

You can read more almost how they work on Wikichip, but let's briefly go through a few things. Each VRM is usually called a phase and multiple phases are required, considering one alone can't supply enough current for a mod CPU (our motherboard has eight VRMs, called an eight-phase organization).

The VRMs are usually managed past a carve up chip, that monitors the device, and switches the modules as for the required voltage. These are chosen multiphase pulse width modulator controllers; Asus calls theirs an EPU! All of these things get quite hot when they're working away, and then they're often covered by a metallic heatsink to assistance dissipate the waste material energy.

Even a standard desktop CPU, such as an Intel i7-9700K, can draw over 100A of current when fully loaded. VRMs are very efficient, but they can't change voltages without some losses; combined with the big current draw, and yous have a good recipe for making things very toasty indeed.

If y'all look support through this article, you'll come across that in that location a couple of VRMs for the DRAM modules, as well, just since they don't draw near the aforementioned corporeality of current as a CPU, they don't get every bit hot (and and so don't need a heatsink).

Those annoying fiddly $.25!

The last connectors to talk almost are the ones for controlling the basic performance of the motherboard and attaching additional devices or extensions. The image below shows a basic set of command, lights, and speaker pins:

Here nosotros accept:

  • 1x soft power switch
  • 1x reset switch
  • 2x LED connectors
  • 1x speaker connector

The power switch is 'soft' because it doesn't actually switch the motherboard on and off; instead, circuits on the board monitor the voltage across the two pins for the switch and when they are connected together (i.e. brusk circuited), the motherboard volition either power on or off, depending on its nowadays status. The same applies for the reset switch, except here the motherboard will ever power off, and so immediately back on again.

Strictly speaking, the reset switch, LED and speaker connectors aren't absolutely necessary simply they exercise assist to provide basic command and information about the board.

Near motherboards have a like array of extra connectors as shown above - from left to right, we take:

  • Audio console connector - if the PC case has headphone/microphone jacks built into it, then they can be continued to the onboard audio scrap
  • Digital audio connector - same as the other audio connector, but for S/PDIF
  • BIOS clear jumper - this allows the BIOS to be reset to default factory settings. There is also a thermal probe connector hidden behind information technology
  • Trusted Platform Module connector - used to aid brand the motherboard and system more than secure
  • Serial Port (COM) connector - an aboriginal interface. Anyone utilize these at all? Anyone? Bueller?

Also plastered across this motherboard, but not shown, are connections for fans and extra USB ports. Non every motherboard will sport all of these merely many do.

Connecting all of this together

Before we finish our await at the anatomy of a motherboard, permit's briefly talk most how all of these devices and connectors are wired together. Nosotros've already mentioned traces just what exactly are they?

Put but, they're small strips of copper. Yous can run into some of them beneath painted black for better looks. Still, this is but a pocket-size number of thousands of traces required. The residue are sandwiched betwixt the multiple layers that brand up the full excursion board.

Unproblematic, cheap motherboards might only have 4 layers, but nearly today have half-dozen or eight -- adding more layers doesn't automatically make things better, though. Information technology's about how many traces there are in total and how important it is to proceed them separated and insulated to prevent them interfering with each other.

Motherboard designers use software to help them work out the best routes for all of these traces; experienced engineers will frequently tweak the layout, though, based on bear witness from practical investigations. What the post-obit video to go a sense of how the routing of traces in printed circuit boards (PCBs) gets processed.

Since motherboards are just large PCBs, it is possible to build your own and if want an idea on how to go nigh this, so have a read of this excellent tutorial of fabricating a PCB.

It's a different story for producing motherboards on an industrial scale, of class, and then to get a sense of how circuitous all of this is, bank check out the two videos below. The kickoff one is how circuit boards, in full general, are designed and manufactured; the 2nd one shows you the main associates process of a typical motherboard. Enjoy!

Final words

So there you lot take information technology: a dissection of a modern desktop PC motherboard. They're big, circuitous circuit boards, packed with processors, switches, connectors, and memory chips. There'southward so much interesting technology in use, but we oftentimes forget about them, as they sit in the cases.

But hopefully you've picked upward things along the fashion and, more importantly, you've got a stack of questions you want to enquire about yours! Well, send them our fashion, using the comments section or visit the CPU & Motherboard department of our forum.

As y'all know we regularly review the latest motherboards out at that place and offer our thoughts every bit to what'southward best for a given budget and platform. Stay tuned for more than anatomy lessons!