Pcie on motherboard: What Are PCIe Slots And Their Uses? [Simplified Guide]

To best understand PCIe slots, here’s an example…

You use Chrome or another browser on your computer every day, don’t you? If you do, you might have installed some browser plugins like IDM, a VPN, an ad-blocker, or anything like that. 

If you can relate to this example, suppose that the Chrome browser is your motherboard. Since Chrome offers the option to install extensions to improve its functionality, your motherboard also gives you that option through PCIe slots. The hardware parts you install are the extensions you install on Chrome.

Got the picture, right? 

By the way, SATA ports are something else you may also be wondering about. Read our guide on what does a SATA port look like to find out more.

Now, what are the different types of PCIe expansion slots, and how to identify PCIe slots? Let’s find out.

What Are PCIe Slot Sizes or Configurations?

There’s a wide range of PCIe slot sizes. But there are 4 common types — and you’ll only encounter these in most cases:

• PCIe x1
• PCIe x4
• PCIe x8
• PCIe x16

These multiples refer to lanes. Generally, more lanes result in a better performance as they ensure a faster connection between the expansion hardware parts and the motherboard.

Number of Transfer Lanes WRT PCie Slots

That’s exactly why high-performance devices like graphics cards go into PCIe x16.

Below is a detailed comparison of different PCIe versions.  

Version	x1(GB/s)	x2(GB/s)	x4(GB/s)	x8(GB/s)	x16(GB/s)
1.0	0.250 GB/s	0.500 GB/s	1.000 GB/s	2.000 GB/s	4.000 GB/s
2.0	0.500 GB/s	1.000 GB/s	2.000 GB/s	4.000 GB/s	8.000 GB/s
3.0	0.985 GB/s	1.969 GB/s	3.938 GB/s	7.877 GB/s	15.754 GB/s
4.0	1.969 GB/s	3.938 GB/s	7.877 GB/s	15.754 GB/s	31.508 GB/s
5.0	3.938 GB/s	7.877 GB/s	15.754 GB/s	31.508 GB/s	63.015 GB/s
6.0	7.877 GB/s	15.754 GB/s	31.508 GB/s	63.015 GB/s	126. 031 GB/s

Uses of Different PCIe Slot Sizes

Here we’ll look into the uses of different PCIe slot sizes:

What are PCIe x1 Slots Used for? 

PCIe x1 slots only offer a single PCIe lane. It suits the small hardware pieces well — like Wifi and sound cards. You cannot install high-end devices like graphics cards on these slots due to low bandwidth. 

What are PCIe x4 Slots Used for?

PCIe x 4 slots come with 4 PCIe lanes and have 4 times the bandwidth of PCIe x1 slots. You can use it for devices like 4k capture cards that take more bandwidth. Similarly, it can also make a fit with the NVMe M.2 SSD expansion card. 

What are PCIe x8 Slots Used for?

PCIe x8 Slots work well with advanced hardware devices like NVMe M.2 expansion cards and high-definition capture cards, and so on. Coming with 8 PCIe lanes, the PCIe x8 slots are double the bandwidth of a PCIe x4 slot. 

What are PCIe x16 Slots Used for?

The PCIe x16 slots are used for high-end hardware expansion cards like graphics cards. Graphics cards have to transfer lots of data every second to the motherboard for video and graphics rendering. Therefore, they require a high-bandwidth slot like PCIe x16 slots. 

Now, the point you should note is that the PCIe slots are also categorized in form of generations other than sizes. Here are the main PCIe generations:

So, What Are PCIe Slot Generations?

Below are the MAIN PCIe generations:

• PCIe 1.0
• PCIe 2.0
• PCIe 3.0
• PCIe 4.0
• PCIe 5.0
• PCIe 6.0

Wondering about the transfer rates and performance of these PCIe slot generations? Well, they double with every next generation (we’ve created a detailed table below). 

Commonly Used PCIe Slot Generations – PCIe 1.0 Through 4.0

Out of the PCIe generations listed above, the four are the common ones: 

• PCIe 1.0
• PCIe 2.0
• PCIe 3.0
• PCIe 4.0

If you’re wondering what sort of performance you’d get on using a PCIe expansion card on any of these generations, it’ll be equivalent to the lowest generation either way.  

For instance, if you connect a 2.0 generation expansion card on a 4.0 generation slot, you’ll only get the performance of the 2.0 generation.

Out of these 4, PCIe 4.0 is a kinda modern generation and a big upgrade that came out in 2017. It offered bandwidth of 64 Gbps and. 

Modern PCIe Generations – PCIe 5.0 and PCIe 6.0

PCIe 5.0 and PCIe 6.0 are the modern standards for PCIe slots.

PCIe 5.0 generation was released in 2019 and carried a remarkable 128 GBps bandwidth. It offered compatibility with the previous PCIe generations and brought forth extra features like:

• Improved electrical system 
• Compatibility with previous PCIe versions

However, the point to note is, only the standard has come out, not the devices. They’re expected to release in 2022. 

Anyway, it is predicted that PCIe 5.0 will only be available for data centers and enterprise-level computers – PCIe will remain the standard for personal systems.

When it comes to the PCIe 6. 0 generation, it doubles the throughput of the previous generation and is also backward compatible. However, companies predict that PCIe 6.0 devices won’t release anytime before the end of 2022. 

Comparison of PCIe Slot Generations

Below is a little comparison of PCIe slot generations that covers their bandwidth, frequency, and gigatransfer rates.

With that said, it’s important to keep your motherboard dust-free to ensure all its components work fine. Read our guide on how to clean a motherboard to learn more about that

Does it Matter Which PCIe x16 Slot I Use?

Yes, the PCIe x16 slot you use does matter. This is because PCIe x16 is the fastest size for PCIe slots and most motherboards have it on the first. The next slots generally are of smaller size. So, it’s recommended to use PCIe x16 slot for maximum bandwidth and performance. 

What to Put in PCIe Slots?

What Can You Put in PCIe Slots

Below are the major devices that can be plugged into the PCIe expansion slots:

1. Video Capture Cards – to convert an analog video signal

2. M.2 NVMe Expansion Cards – to add additional storage 

3. TV Tuner Cards – to receive television signals

4. Wireless + Bluetooth Network Cards – for wireless internet

5. Graphics Cards – for better graphical power

6. SATA Expansion and RAID Controller Cards – to add more optical drives

7. Sound Cards – to produce sound on the computer

8. Ethernet Network Cards – for wired Ethernet connections

9. Port Expansion Cards – for additional ports on the computer

10. Riser / Splitters – to extend a slot for an I/O card

Are PCIe Slots Compatible With Slot Cross?

The slot cross-compatibility refers to installing a device with a lower lane coin into a slot with a higher lane count.

Thankfully, the PCIe system is designed in a way to make this possible. 

For instance, if you have an expansion card (like a Wifi card) that is PCIe x4 (4 lanes) and the only slot available is PCIe x8, then it might be possible to install the card into this slot. In fact, the expansion card will work properly. 

However, you’ll get the lowest bandwidth of either slot or the expansion card. Let me explain:

Using an expansion card with a lower lane count compared to the lane count of the slot you’re putting it into will result in the bandwidth of the slowest hardware part.  

So, if you put a PCI x1 card into a PCI x4 slot, the performance will be equivalent to PCI x1 at the end of the day. 

Are PCIe Slots Backward Compatible?

Other than the cross-slot compatibility, backward compatibility is another major highlight of the PCIe standard. 

Meaning you can install an expansion card with a higher lane count into a slot with a lower lane count, as long as the card fits (depending on the size).

For instance, if a card with PCIe lane x8 is put into a PCIe x4 slot, it might work just fine. 

Another point to note is, these compatibility rules also apply to PCIe versions. So, you can put a PCIe 2.0 device into PCIe 4.0. But again, the performance is equivalent to the lowest connection. 

Sorry to disturb you but determining how many SATA cables you want can be tempting. Read our guide on how many SATA cables do I need to find out more about that.

How to Identify PCIe Slots 

The best way to identify PCIe slots is by determining the size of PCIe slots on your motherboard. Simply open your PC case and know that the first PCIe slot is a PCIe x16 in most cases. 

After that, you might find a PCIe 8x slot and then a PCIe 4x. However, the order can be slightly (or significantly) different depending upon the motherboard. 

Furthermore, you can also look into the image below for convenience:

How to Identify PCIe Slots

Real-Time Example for PCIe Slot Configuration

How to Identify PCIe Slots

The above image is a live example of how to determine PCIe slot configuration. 

As you can see, the first PCIe slot is the x16 size while the next one is x8. Now, these do come in the same sizes but have different lane counts. 

Next to the PCIe, x8 configuration is the PCIe x4 configuration which follows PCIe x1. 

Most of the ATX standard motherboards come with such a configuration order. But the case is not always the same. Some motherboards might also have a different order. 

For instance, a high-end motherboard could have a PCIe x32 configuration at the start. Similarly, an old-school motherboard could have the PCIe 8x configuration. It depends upon many factors of the motherboard like form factor, budget, and so on. 

Anyway, below are the images of a few motherboards with different configuration orders:

Motherboard 1:

Motherboard 1 Example

Motherboard 2:

Motherboard 2 Example

Video for Understanding PCIe Standard

With all of that said, below is a helpful video you can go through quickly, for understanding what PCIe Express is:

Other Motherboard-Related Guides

Does DDR5 RAM Work on the DDR4 Motherboard? — Find out whether DDR5 RAM is going to be backwards compatible or not.

How Can I Troubleshoot a Motherboard? — Discover the 10 most effective ways to troubleshoot am motherboard with minimal effort.

What are Standoffs on Motherboards? — Learn what motherboard standoffs are why they’re so important, and where you can get them.

Final Words

That’s pretty much it. I hope this guide helped you find out what are PCIe slots and their uses. To recap, PCIe slots work as expansion slots that let you install further hardware on the motherboard. It could be a graphics card or a port expansion card.

With that out of the way, do share the article if you liked it. 

What part did you find the most interesting? Let me know in the comments. 

What are PCIe Slots and Their Uses?

PCIe slots allow you to add expansion cards on your motherboard in order to provide additional functionality to your PC. They come in various sizes, each designed for a specific category of expansion cards. Whether you want to add a graphics card for gaming, a WiFi network card, or a dedicated sound card, you use the PCIe slots.

There are two basic interfaces that a computer uses to add more components, SATA and PCIe. SATA is a slower interface and is used for spinning hard disks primarily these days and also for CD/DVD drives.

PCIe, on the other hand, is far superior in terms of transfer rate and thus supports high speed components ranging from NVMe SSD all the way to GPUs.

As mentioned earlier, there are different sizes of PCIe slots and knowing how they function and what differentiates one slot from the other is crucial for PC builders.

Here we will talk in depth about PCIe in general and PCIe slots in particular.

TABLE OF CONTENTS

What Does a PCIe Slot Look Like?

In order to understand what PCIe slots look like, a picture would be the best guide.

Image: Motherboard with two x1 slots (white) and two x16 slots (blue)

As you can see in the image above, PCIe slots come in different sizes. They are distinguished mainly by their PCIe lane count.

Also Read: What Does a PCIe Slot Look Like? – In Depth Look

What are PCIe Slots, Lanes, Generation?

There are a few important characteristics of PCIe interface you need to understand in order to understand and utilize the slots properly i. e

• What PCIe is
• PCIe Lanes
• PCIe Slot Sizes and Motherboard Configuration
• PCIe Generation

let us start from the beginning.

What is PCIe?

PCIe stands for Peripheral Component Interconnect Express, and it is an internal bus interface standard that is used to connect internal high-speed components to your desktop motherboard.

There is a list of things that you can attach to the PCIe slots. We have summarized them here: 10 Things That Can be Plugged in PCIe Slots here.

PCIe slots have PCIe lanes hardwired to them for transporting data.

PCIe Lanes in Brief

Understanding PCIe lanes is very important for understanding what PCIe slots are and how they work.

A PCIe lane is basically the path through, or the connection through, which data is transported to and from the slot and the CPU. Different slot sizes have different amount of PCIe lanes.

The more PCIe lanes a slot has, the higher is its throughput rate (speed) and the more demanding expansion cards it can support.

There are four types of PCIe lane configuration you can find on PCIe slots i.e x1, x4, x8 and x16.

In most cases, the number after “x” tells you the number of PCIe lanes the slot has. The x16 slot, however, is a bit confusing to understand as the number 16 here after “x” does not always mean 16 lanes; more on this below.

Therefore, a PCIe x4 slot has 4 PCIe lanes or it can support a device with a throughput rate requirement of upto 4 PCIe lanes such as an NVMe SSD expansion card.

You must note that the amount of PCIe lanes a PC has in total are generally dictated by the CPU and the Motherboard. A PC DOES NOT have unlimited lanes.

The total number of PCIe lanes a PC has can be found by looking at CPU specsheet and the motherboard CHIPSET specsheet.

Image: Number of PCIe lanes provided by the Intel Core i7-10700K. Source: Intel.com

Most mainstream processors have 16-24 PCIe lanes with only the extreme and premium processors reaching 44 or more dedicated PCIe lanes.

Motherboards also provide PCIe lanes, however, not all of them are user accessible. For instance, Intel Z490 motherboard has 24 PCIe lanes, however, depending on how the board is configured you could only have 4 to 6 lanes available for use and the rest would be reserved for internal components like SATA ports, USB ports etc.

Therefore, with a configuration of 16 CPU lanes + 4 provided by the motherboard chipset, you will have a total of 20 PCIe lanes to use in total.

With this you can, for example, add a single x16 graphics card and a single x4 NVMe SSD Card.

Or perhaps you could add a single graphcis card (x16), a WiFi Card (x1), a FHD video capture card (x1) and still have 2 PCIe lanes. This all depends upon how the motherboard is configured and what type of slots it provides.

Again, you can find the number of CPU and motherboard PCIe lanes in their respective data sheets. The following guides detail PCIe lanes in depth.

• What are PCIe Lanes? – Beginners Guide
• How to Check How Many PCIe Lanes Do I Have?

PCIe Slot Sizes and Configuration

Image: Different form factors follow a different PCIe slot configuration.

All modern desktop PC motherboards come with at least one PCIe slot that will allow you to hook up extra devices like VGA cards, Sound Card, RAID controllers etc to extend your PC’s functionality.

The only difference is that not all boards will come with the same number, type, or even version of PCIe slots.

Motherboard Form Factor Matters in PCIe Slot Configuration

The number of PCIe slots you have also depends a lot upon the motherboard form factor in addition to the total amount of PCIe Lane count, as covered earlier.

An ATX motherboard, for instance, typically offers a whole lot of PCIe slots in different sizes. A Mini-ITX motherboard, on the other hand, being the smallest motherboard for desktop computers, offers only a SINGLE PCIe x16 slot despite supporting more than 16 PCIe lanes!

Different PCIe Slot Sizes and Their Uses

There are typically two PCIe slot sizes found on almost all commercial motherboards:

• x1: This offers only a single PCIe lane. It is suitable for weaker and smaller cards like a WiFi card or a sound card.
• x16: This is the largest slot found on a motherboard and also the most confusing to understand. More on this below.

Also Read:

• Does it Matter Which PCIe x16 Slot I Use?
• Can You Plug A PCIe X1 Into an X16 Slot?

The Curious Case of the x16 Slot

Image: Gigabyte GA-P67A-UD3 has two x16 slots (Blue), but the second x16 slot only offers x4 lane.

Many time you will find an x16 slot wired to only x8 or even just x4 lanes! Always refer to the specsheet to understand the true lane count of the slot.

If you only have a single x16 slot on your motherboard, then this will almost definitely have 16 PCIe lanes coming directly from the CPU.

If you have MORE than one x16 slot, however, then the second x16 slot would either be operating in x8 or x4 mode. This is due to the limited nature of PCIe lanes you have available on your PC. A typical PC with 20 to 24 PCIe lanes cannot have two full x16 slots as that would take the lane count to 32!

In summary, there are three configuration for an x16 slot:

• x16(x4): This slot has the physical size of an x16 slot but is hardwired to only 4 lanes. This slot is used for devices like an NVMe M.2 SSD expansion slot or 4k video capture card, that require a higher bandwidth than an x1 slot an offer.
• x16(x8): These are found on premium motherboards for dual graphics card builds. Again, this slot has the physical size of an x16 slot, but only has four lanes connected to it.
• x16(x16): A true x16 slot that connects to x16 lanes is found on almost all motherboards. They have the highest throughput rate and thus these are typically occupied with graphics cards. 

Also Read:

• How Many PCIe Slots Do I Need?
• What are PCIe x1 Slots Used For?

PCIe Generation and Slot Performance

The overall performance of the PCIe slot is significantly affected by its PCIe version.

Each newer generation of PCIe interface DOUBLES the per lane speed. So for instance while a single PCIe v3.0 lane (x1) has a throughput of 985 MB/s, a single PCIe v4.0 lane (x1) has double the throughput i.e 1,969 MB/s.

The following table summarizes PCIe speeds across varios generation.

Version	x1 (GB/s)	x2 (GB/s)	x4 (GB/s)	x8 (GB/s)	x16 (GB/s)
1.0	0.250	0.500	1.000	2.000	4.000
2.0	0.500	1.000	2.000	4.000	8.000
3.0	0.985	1.969	3.938	7.877	15.754
4.0	1.969	3.938	7.877	15.754	31.508
5.0	3.938	7.877	15.754	31.508	63.015
6.0	7.877	15.754	31.508	63. 015	126.031

A newer PCIe version has a lot of ramification. A motherboard with a newer PCIe slot can support newer gen devices such as faster NVMe SSDs and more powerful graphics cards. 

Also Read: PCIe 3.0 vs 2.0 – What is the Difference?

Slot Cross and Backward Compatibility

The best part about the PCIe standard is the cross and backward compatibility of different slots with different PCIe devices and generation.

Basically, if you have an x4 slot and the device you want to install is an x1 device, you won’t need any special software to work around the hurdle.

Plugging in a lower lane count expansion card into a higher lane count slot will let the device work as intended albeit with the cumulative bandwidth of the slowest component.

In other words, installing a weaker x1 device into an x4 slot will work, however, the x1 device will NOT get any performance boost.

Likewise, a higher lane count expansion card can go into a small lane count slot as long as it can fit. So, you can plug your x16 graphics card into an x8 slot and it will still work, but at the speed of the x8 slot; therefore, there can be some performance reduction.

This compatibility also cuts across the versions of PCIe so a PCIe 3.0 device can work in a PCIe 2.0 slot and vice versa.

The only caveat is that the configuration will work at the lowest common speed between the slot and the component.

Image: PudgetSystems.com. Comparison of how RTX 3090 (PCIe 4.0 Device) and Titan RTX (PCIe 3.0 Device) performs on different PCIe generations. An impact can be seen on performance in DaVinci Resolve (video editing software).

Here you can see that using a graphics card on an older gen slot can result in some performance reduction. 

Also Read:

• Can I Use a PCIe 3.0 Card in a 2.0 Slot?
• Can PCIe X1 Card Fit in X4 Slot?

Practical Example of Understanding PCIe Slot Configuration

Image: MSI MPG Z490 Gaming Carbon WiFi

The motherboard above is an excellent example of how PCIe slots are configured on a typical mid range full ATX motherboard.

You will notice that the motherboard above has 3 PCIe x16 slots (two in silver color and there is one black colored x16 slot at the very bottom that may be hard to see).

Due to the Lane limitation, as mentioned earlier, this motherboard has been specified to be used in x16/x0/x4 OR x8/x8/x4 modes.

In other words, you can use the motherboard in two modes.

Mode 1: ( x16/x0/x4)

• Top slot working in x16 mode i.e with a single Graphics Card.
• Middle slot empty
• Bottom slot working in x4 mode i.e for an NVMe SSD expansion card for instance.

Mode 2: (x8/x8/x4)

• Top slot working in x8 mode i.e with a Graphic Card
• Middle slot working in x8 mode i.e with another Graphics Card
• Bottom slot working in x4 mode i.e for an NVMe SSD expansion card for instance.

Here you will notice that mode 2 is great for SLI or Crossfire setup where you have two graphics cards. The only issue is that both graphics card will work at reduced performance due to half the supported bandwidth. The difference as tested, however, between running the card in x16 or x8 is only marginal.

This motherboard also has two smaller x1 slots that can be used for smaller cards as well.

To get FULL 2 x X16 slots you will need to get a workstation grade CPU from the Intel X-series or AMD Threadripper series and also a workstation grade motherboard to give the higher number of PCIe lanes required to run the two or more x16 slots at full bandwidth.

Also Read: Do Laptops Have PCIe Slots?

A Brief History of the PCIe Slot

Image: PCIe (Left) vs PCI (Right). Source: How Stuff Works

Several other slots were used to connect expansion cards to the motherboard before the introduction of the PCI slot in 1992 by Intel.

For example, before the introduction of the original PCI standard, ISA (Industry Standard Architecture) bus slots were the main interface for connecting expansion cards.

ISA slots, unfortunately, were longer and had slower data transfer speeds.

PCI standard was created to alleviate the shortfalls of the previous buses that were at the time much slower and hence inefficient for the growing throughput demand of the expansion cards.

The PCI standard became more widespread towards the end of the 90s and saw some improvements. However, it was replaced by the more efficient PCI Express standard that has been in use since 2002.

Difference Between PCI vs PCIe

Image: Shows the difference between the older PCI standard using shared bus interface as compared to the newer PCIe that uses serial direct interface.

PCIe makes use of independent transfer lanes instead of the shared bus that the older PCI standard uses. The ability to transfer data in multiple lanes means an overall increase in bandwidth.

The main difference between the two typologies was that the PCI used Parallel where as the PCIe used Serial architecture. Basically with the PCI parallel architecture, each connected device shared the same bus.

The limitation here was that since every device shared the same bus, when a higher number of devices where to be connected, they would have to wait for the bus to free up to send and receive data.

PCIe, on the other hand, completely changed the topology to a serial architecture where each and every device has its own dedicated bus now.

The speed difference between the two interfaces was phenomenal. While PCI topped at 2.13 GB/s (bi-directional bandwidth) with its final PCI-X 2.0 version released in 2002, the PCI Express v1.0 on the other hand, released in 2002, had a total bi-directional bandwidth of 8GB/s. Thus drastically improving on its predecessor.

The current v4.0 has a throughput of around 32 GB/s and bi-directional bandwidth of around 64 GB/s!

Also Read: What are USB Headers?

Final Words – Do You Need to Use PCIe Slots?

The key takeaway from here is that a PCIe slot is the primary interface through which you connect high speed expansion cards that add functionality to your PC.

Here we talked extensively about what are PCIe slots by looking into PCIe lanes, slot configuration and sizes, and PCIe version.

There are, of course, chances that you may never have to use PCIe slots at all for your system.

For instance, if your CPU comes with an integrated graphics card and if your motherboard comes with display output ports, a soundcard, and a network card – like most motherboard these days do – then chances are that you may never have to add another expansion card anyways.

This is particularly true if you are an average home or office user. Basic PC for home use have everything you need installed onboard the motherboard and the CPU itself. Only professionals and gamers may require the use of PCIe slots for adding more functionality to their system.

PCI Express — differences between x1, x4, x8, x16

Author Roman Kolotravov To read 7 min Views 22.3k. Posted by June 12, 2018

What’s interesting in this article:

1. What is a PCI Express bus?
2. The impact of the number of lanes on throughput
3. Types of devices using PCI Express x2, x4, x8, x12, x16 and x32
4. PCI-E port and lane sizes can vary

The PCI Express standard is one of the foundations of modern computers . PCI Express slots have long taken a firm place on any desktop computer motherboard, supplanting other standards such as PCI. But even the PCI Express standard has its own varieties and connection patterns that differ from each other. On new motherboards, starting around 2010, you can see a whole scattering of ports on one motherboard, labeled as PCIE or PCI-E , which may differ in the number of lines: one x1 or several x2, x4, x8, x12, x16 and x32.

So, let’s find out why there is such confusion among the seemingly simple PCI Express peripheral port. And what is the purpose of each PCI Express x2, x4, x8, x12, x16 and x32 standard?

What is a PCI Express bus?

Back in the 2000s, when the aging PCI (ext. — Peripheral Component Interconnection) standard moved to PCI Express, the latter had one huge advantage: instead of the serial bus, which was PCI, a point-to-point access bus was used. This meant that each individual PCI port and the cards installed in it could take full advantage of the maximum bandwidth without interfering with each other, as they did when connected to the PCI . In those days, the number of peripherals inserted into expansion cards was plentiful. Network cards, audio cards, TV tuners and so on — all required a sufficient amount of PC resources. But unlike the PCI standard, which used a common bus for data transfer with several devices connected in parallel, PCI Express, if considered in general, is a packet network with a star topology.

PCI Express x16, PCI Express x1 and PCI on the same board

In layman’s terms, imagine your desktop PC as a small shop with one or two vendors. The old PCI standard was like a grocery store: everyone was waiting in line to be served, having problems with the speed of service, limited to one seller behind the counter. PCI-E is more like a hypermarket: each customer moves for groceries along their own individual route, and several cashiers take orders at the checkout at once.

It is obvious that the hypermarket outperforms a regular store in terms of service speed by several times, due to the fact that the store cannot afford the throughput of more than one seller with one checkout.

Also with dedicated data lanes for each add-on card or integrated motherboard components.

Not about PCI, but also interesting:

? Why is it important to set a BIOS password, and how to do it?

? Dealt with all kinds of computer ports/interfaces and their adapters

The impact of the number of lines on throughput

Now, to expand our metaphor with a store and a hypermarket, imagine that each department of the hypermarket has its own cashiers reserved only for them . This is where the idea of ​​multiple data lanes comes in.

The

PCI-E has gone through many changes since its inception. Currently, new motherboards usually use version 3 of the standard, with the faster version 4 becoming more common, with version 5 expected in 2019.year. But different versions use the same physical connections, and these connections can be made in four basic sizes: x1, x4, x8 and x16. (x32 ports exist, but are extremely rare on regular computer motherboards).

The different physical sizes of the PCI-Express ports make it possible to clearly distinguish them by the number of simultaneous connections to the motherboard: the larger the port physically, the more maximum connections it can transfer to or from the card. These compounds are also called lines . One line can be thought of as a track consisting of two signal pairs: one for sending data and the other for receiving.

Different versions of the PCI-E standard allow different speeds on each lane. But generally speaking, the more lanes there are on a single PCI-E port, the faster data can flow between the peripheral and the rest of the computer.

Returning to our metaphor: if we are talking about one seller in the store, then the x1 lane will be this only seller serving one client. A store with 4 cashiers already has 4 lines x4 . And so on, you can list cashiers by the number of lines, multiplying by 2.

Various PCI Express cards

Types of devices using PCI Express x2, x4, x8, x12, x16 and x32

For PCI Express 3. 0 version, the total maximum data transfer rate is 8 Gb / s. In reality, the speed for the PCI-E 3 version is slightly less than one gigabyte per second per lane.

Thus, a device that uses a PCI-E x1 port, such as a low-power sound card or Wi-Fi antenna, will be able to transfer data at a maximum speed of 1 Gbps.

A card that physically fits into a larger slot — x4 or x8 , such as a USB 3.0 expansion card, will be able to transfer data four or eight times faster, respectively.

PCI-E x16 ports are theoretically limited to a maximum bandwidth of about 15 Gb/s. This is more than enough in 2017 for all modern graphics cards developed by NVIDIA and AMD.

Most modern graphics cards use PCI Express

The PCI Express 4.0 protocol already allows 16 GT/s, while PCI Express 5.0 will use 32 GT/s.

But there are currently no components that can use this amount of bandwidth at maximum bandwidth. Modern high-end graphics cards typically use the x16 PCI Express 3. 0 standard. It makes no sense to use the same bandwidths for a network card that will use only one line on an x16 port, since the Ethernet port is only capable of transmitting data up to one gigabit per second (which is about one eighth of the bandwidth of one PCI-E lane — remember: eight bits in one byte).

There are PCI-E SSDs on the market that support the x4 port, but they look like they will soon be superseded by the rapidly evolving new M.2 standard. for SSDs that can also use the PCI-E bus. High-end network cards and enthusiast hardware such as RAID controllers use a mix of x4 and x8 formats.

PCI-E port and lane sizes can vary.

This is one of the more confusing PCI-E challenges: a port can be x16 sized, but not have enough lanes to pass data, for example, just x4. This is because even though PCI-E can carry an unlimited number of individual connections, there is still a practical limit to the bandwidth of the chipset. Cheaper motherboards with more budget chipsets may only have one x8 slot, even though that slot can physically accommodate an x16 form factor card.

In addition, gamer-focused motherboards include up to four full x16 PCI-E slots and as many lanes for maximum throughput.

For example — ASUS X99-DELUXE II RTL. Motherboard with 4 PCI-E with x16

Obviously, this can cause problems. If the motherboard has two x16 slots, but one of them has only x4 stripes, then adding a new graphics card will reduce the performance of the first one by as much as 75%. This, of course, is only a theoretical result. The architecture of the motherboards is such that you will not see a sharp drop in performance.

A proper configuration of two graphics cards must use exactly two x16 slots if you want maximum comfort from a tandem of two video cards. The manual at the office will help you find out how many lines on your motherboard this or that slot has. manufacturer’s website.

Sometimes manufacturers even mark the number of lines on the motherboard textolite next to the slot:

Labels on the motherboard PCI Express x1 and x4

You need to know that a shorter x1 or x4 card can physically fit into a longer x8 or x16 slot. The contact configuration of the electrical contacts makes this possible. Naturally, if the card is physically larger than the slot, then it will not work to insert it.

So remember, when buying expansion cards or upgrading current ones, you must always remember both the size of the PCI Express slot and the number of required lanes.

PCIe lanes — How many do you need for a high workload

When choosing a motherboard and processor for a PC build, most builders overlook choosing the right number of PCIe lanes. Identifying them is not only critical for a new build, but also reduces the need for future updates, saving your installation for the future.

While the first thing that comes to mind when you think of PCIe might be the slot on your motherboard that you plug your graphics card into, is a much wider technology than .

The PCIe lanes allocated to a component can seriously impact tasks such as multi-GPU rendering, as the bandwidth of these lanes limits the maximum performance of the component connected to the PCIe slot.