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On the surface, a motherboard appears to me like it's not a "performance" part like a CPU or a graphics card. The purpose, at least from my understanding, is to connect the various hardware parts together, as well as offer a handful of USB and other interface ports on the back.

As such, when buying a motherboard, any motherboard that supported my CPU's socket seemed to be as good as any other. What exactly is the difference between them? What should I look out for when determining whether a motherboard will fit my needs?

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    The performance of a streaming service is defined by server and client computers, any network connection able to connect the two is as good as any other... Oh wait! Nov 10 '20 at 13:10
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    Features, features, features, support, and longevity. How many USB ports do you want? How many RAM slots will you need? How fast do you want your RAM to go? How large of a RAM stick do you wish to use (8, 16, 32, 64 GB)? Do you plan to overclock the CPU? How many SATA or NVMe ports do you want? How long do you expect the capacitors to last before they start leaking? How many options do you expect from the BIOS? How many PCIe slots do you want? If a bottom of the barrel motherboard develops a BIOS issue then it tends to go unresolved because the manufacturer doesn't care about a $35 mobo.
    – MonkeyZeus
    Nov 11 '20 at 13:46
  • If you care about nothing mentioned above then yes a bottom of the barrel mobo will happily run a CPU on its socket.
    – MonkeyZeus
    Nov 11 '20 at 13:48
  • The existing answers are detailed and correct but very shortly: there are significant differences in the supported periferals, the number and supported speed of PCIe, M.2 and similar add-ons (primarily determined by the chipset but not only, two MBs with the same chipset might still have differences in this regard), possible differences in network speed supported, presence or absence of some additional units (eg. onboard wifi), down to differences of the number of some connectors (both on board and on the IO panel).
    – Gábor
    Nov 11 '20 at 16:46
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This question actually comes down to what a modern motherboard actually does. I agree, that in many (if not most of the) cases the answer is "provide the glue between well-specced components along the lines of a reference implementation". So let's look for differentiating aspects:

  • Mechanical: Since the mainboard decides the position of the extension slots, it bears final responsibility, how many and which extension cards (e.g. GPUs) can be used.
  • On-board devices: There is no universal answer - it depends on the use case whether you need or want additional SATA or SAS ports, a fancy sound device, more Ethernet ports, etc.
  • Build quality: For me this is the most important aspect - if you drive your hardware to its analog limits (i.e. temperature, frequency, etc.) you want to have the most reliable components assembled in the most reliable way. Especially capacitors come in a wide variety of qualities and they do make a price difference. The engineering hours to know where to put them also don't come easy.
  • Software: A board is useless without its Firmware (UEFI, BIOS, Setup utility, etc.) depending on its implementation it will not only allow you more or less headroom e.g. when overclocking, it will also have important influence if you want to use something else than Windows. And just as other Software, the Firmware might need an update here or there when new parts become available or a combination of factors is found, that triggers a not-yet-known error

Basically, it's a matter of trust - are you comfortable with giving this or that vendor the responsibility to keep your rig fast and reliable? This is, why different brands and different product lines within those brands exist.

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    The expansion slots isn't just a mechanical issue. The board also determines the electronic topology of how those expansion cards are connected. Are there any PCI slots? How many PCIe lanes go to which PCIe slot, and are those lanes with dedicated bandwidth from the route hub, or are the multiplexed through a potentially bottlenecking multiplexer. Its unlikely to be relevant with a normal single SSD + single graphics card build, but on more complex builds that can be a factor. Nov 9 '20 at 1:00
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    Finally, one factor that is quite significant in modern boards: Asthetics. If you build a case with a glass side, then the aesthetics of the motherboard can be a part of chosing the board. Nov 9 '20 at 1:01
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    There is also a distinction between pcie muxes and pcie switches. In general, most motherboards will not include discrete pcie switches (though the CPU and chipset can act as PCIe switches), but is quite common to use muxes to 'steal' lanes from one slot to supply a different slot (for example, it is common to use pcie muxes to select whether the first x16 actually gets 16 lanes, or if 8 of those lanes get routed to the second x16 slot so they both run x8). Nov 9 '20 at 4:55
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    @user1937198 Don't forget the LEDs, those make everything go faster. At least, why else are there so many of them on the average 'gaming' motherboard nowadays...
    – Mast
    Nov 9 '20 at 6:47
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    One aspect that has not been mentioned so far is CPU power regulation. Modern CPUs have multiple power inputs (for individual cores or even parts of cores, and functionalities like memory controller and iGPU) and their power needs can vary independently. Different vendors make different choices on number of PWM phases, type of power MOSFETs and the PWM controllers. A lot of this is mostly important when overclocking, but pairing a power-hungry processor with a motherboard that has the cheapest possible power regulation is not a recipe for reliability either...
    – telcoM
    Nov 9 '20 at 8:07
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Here's a list of a few of the main differences when it comes to consumer motherboards:

Chipset

Each line of CPUs has a list of chipsets which it is compatible with. Some of these chipsets provide the ability to overclock the CPU while others don't. Some chipsets provide more features and integrated peripherals than others, such as more 10 Gbps USB ports, more SATA ports, integrated RAID boot support and virtualization support.

Here is an example comparison table for some of the chipsets AMD offers for their latest CPUs as of 2020-11, showing how some have more features enabled than others:

AMD 500 Series Chipsets

The chipset is an integral and irreplaceable part of whichever motherboard you opt for. If you don't need high bandwidth PCIe lanes, or overclocking support, you may find you can save money with a lower-end chipset board. Otherwise, if you're setting up a moderately high-end gaming PC, opting for a higher-end chipset that at least supports overclocking is a good idea.

Form factor

Most consumer motherboards today come in four sizes: EATX, ATX, microATX and Mini-ITX.

EATX, ATX, microATX, Mini-ITX

Generally speaking, each size is just as capable of running whatever hardware it hosts without any compromise in performance, but smaller motherboards may have fewer PCIe slots, fewer RAM slots and fewer ports and peripherals.

Smaller motherboards can be great if they support everything you need, as they allow you to use smaller cases which may be easier to transport and less of an eyesore in the room they're in.

Power delivery

Close to the CPU on any motherboard is a part of the circuit called the "VRM" (voltage regulator module). This is implemented with a multiphase buck converter, containing a collection of inductors, MOSFETs and capacitors. The VRM is crucial to provide a stable voltage to the CPU while it draws a very high current. Generally speaking, more phases in the VRM provides better power delivery, as well as use of higher quality components.

VRM on a motherboard

If you're not doing anything like overclocking your CPU, you may find it completely unnecessary to even consider what your motherboard provides by way of a VRM to your CPU, however if you are interested in overclocking and running a high-end gaming PC, VRMs are a commonly discussed topic which is worth doing some research into.

I am also aware of at least one cheaper motherboard, specifically for AMD Threadripper CPUs, which is limited in its support to only the lower end CPU models in what would otherwise be its full supported CPU series, simply because they don't provide a sufficient VRM for running the higher end processors.

PCIe slots

If you look carefully at the specifications of your motherboard, you should find they describe what exactly each PCIe slot supports. While you might think you could just plug any card you want into any slot that fits, and more PCIe slots are better, in practice, standard consumer CPUs (besides HEDT CPUs such as Intel Core X series, AMD Threadripper) only have a limited number of PCIe lanes usable. Intel boards typically only have 16 lanes, which is all the lanes of a single GPU, while AMD boards typically only have 20 available lanes, which is enough for one GPU and one NVMe SSD. This means that if you want to connect, for example, two GPUs at once, you need the lanes to be split into two x8 lane slots. This would normally still give plenty of bandwidth for GPUs, besides maybe some GPGPU workloads. You should pay careful attention to exactly how the slots are configured if you're intending on doing this, as not all motherboards will bifurcate the main 16 lanes into two 8-lane slots, and instead might only support the full 16 lanes going to the first slot, leaving the other slot with just 4 lanes physically connected to it, connected to the auxiliary PCIe lanes provided by the chipset (contended for bandwidth).

If you want three moderately high-bandwidth PCIe peripherals connected to your motherboard (e.g. two GPUs + one SAS HBA for hard drives), it's much harder than it looks to find a motherboard which properly supports all these at once. Currently, there are just a few PCIe 4.0-supporting AMD motherboards which allow for running three PCIe 3.0 x8 cards at once with minimal bandwidth contention.

One cool feature provided by a few Mini-ITX motherboards, which only have a single PCIe x16 slot onboard, is the ability to use a passive PCIe riser card which bifurcates the slot into two x8 lane slots, which can be used to get a very compact dual-GPU PC. It is however quite difficult to find out if various motherboards support this or not.

The main thing to note with PCIe slots is the physical width of the slot does not necessarily determine the number of lanes actually wired to it and usable.

Most M.2 slots are also just another form factor of PCIe slots which also require PCIe lanes from either the CPU or chipset routing to them. Depending on your needs, you should pay close attention to whether using an M.2 slot for a PCIe NVMe drive would conflict with also using one of the main PCIe slots on the board.

Onboard peripherals

Some motherboards provide a collection of useful onboard peripherals which aren't provided by just the CPU and chipset, such as extra 10 Gbps ethernet cards, SAS HBAs or RAID controllers, WiFi cards and high quality sound cards.

Aesthetics

Some people have different preferences as to how they want their motherboard to look, particularly when setting up flashy gaming PCs with windowed cases. Some motherboards are different colours and some have lots of flashy rainbow LEDs. Some also provide headers for controlling external addressable RGB LED strips with onboard firmware.

Fans and cooling

Motherboards typically have multiple integrated PWM fan control headers, which allow case fans + CPU fans to be wired directly to the motherboard, which get controlled by an onboard microcontroller. Some boards will come with more fan headers than others and some may not have PWM control support for all the fans. Some motherboards also provide voltage regulation for controlling fan speed as an alternative for slowing down non-PWM fans. Different boards by different manufacturers may have better or worse options in their settings for adjusting fan curves and linking fan speeds to different temperatures, including the CPU temperature and external temperature sensor pins.

High end motherboards with lots of fan headers, as well as additional sensor pins, may be a good choice for people opting for a custom water cooling solution for their CPU and GPUs, where they may have a sizable array of fans which cool radiators, and they may have water temperature and flow rate sensors.

Another thing to note is a few motherboards have integrated fans to cool parts such as the chipset, which some people may find to be slightly unfavourable and noisy compared to fanless motherboards.

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    Great answer! But there's one more parameter that recently caught me off guard: support for clocking speeds of different RAM sticks. I bought ASRock X370 Pro4 motherboard and, uhh, G.SKILL Flare X 16GB [2x8GB 3200MHz DDR4 CL16] RAM sticks, and it turned out that I bought one of the few G.SKILL sticks that the motherboard doesn't support, so instead of them working from the get-go at 3200MHz, they're stuck at 2133MHz. The motherboard is totally capable of supporting paired sticks at 3200MHz, but not mine.
    – Dragomok
    Nov 9 '20 at 19:48
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    @Dragomok - Considering what I just spent on a new computer, I'll be rocking 2667MHz for quite a while (max for my MB). I'd be pissed off if it wasn't so awesome. 3200MHz, eh? Given that the OP says 'the CPU will fit', the paramount consideration is the ram clock speed, and secondarily: the closest your wallet can get you to a MB that supports 4,600MHz. Everything else is tertiary, with the caveat that it all has to physically fit.
    – Mazura
    Nov 10 '20 at 2:25
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    One more thing: Power consumption of the motherboard itself. As far as I’m aware especially PCIe4 chipsets are quite power hungry (some even come with a fan).
    – Michael
    Nov 10 '20 at 9:19
  • You say, "Currently, there are just a few PCIe 4.0-supporting AMD motherboards which allow for running three PCIe 3.0 x8 cards at once with minimal bandwidth contention." Which motherboards are they?
    – Toothbrush
    Nov 10 '20 at 13:19
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    You may want to add that M.2 slots are not all equal. In some cases the M.2 slot may be reduced to SATA only, if there is a 2nd PCIe card present next to the GPU. If your M.2 SSD doesn't do SATA (and many don't) it won't work at all. I've also seen plenty of motherboards with 2 M.2 slots, but with the caveat that if both were used simultaneously they both were reduced to 2 PCIe lanes in stead of 4. In other words: You can add a 2nd M.2 SSD, but BOTH SSDs get a performance reduction if you do.
    – Tonny
    Nov 11 '20 at 15:59
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Its always good to look if a motherboard have the latest of things. Like USB 4.0, WIFI 6, BlueTooth 5.0, PCI 5.0, DDR5 etc. Some if these are coming now some later. But also go back to your applications. Game, software development, data bases or what? Read about them and learn where to put your money. For me doing BI and database its memory and fast communication with hardrives/SDD. And Intel i5 is enough but some motherbords/Notebooks have limitations on intalling certain DDR modules. As said before check wich are compatible. I could need 4x16GB (There isnt that many and fast speeds and I will maybe wait for DDR5. But You can always wait for the latest :-)

Please share your experience choosing right depending your application!

Yuo need quiet pc? There is motherboards made of chipsets for Notebook you can buy, usually in small format. Good if you work long hours in front of PC. You can of course build a quiet PC with various fabs/weater cooling etc. Over clocking needs noisy fans!

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