Difference Between PCIe x1 vs x16

Those who are new to PC building in general and to the PCIe interface in particular, the jargon can seem a bit confusing and daunting at times. What does the “x” mean and what is the difference between PCIe x1 vs x16? Is PCIe x1 slower or faster than PCIe x16?

Well, in a nutshell, a PCIe x1 slot has a single PCIe lane, whereas, a PCIe x16 slot can have 4, 8, or 16 lanes depending upon how it is configured. Therefore, as far as the performances goes, a PCIe x16 slot can handle far more demanding expansion cards as compared to a PCIe x1 slot.

PCIe interface is a very important interface to understand for any PC builder particularly when buying a new PCIe expansion card.

While I have covered the nitty gritty details of the PCIe interface in detail here at PCGuide101, in this article, I will particularly talk about the difference between PCIe x1 and x16. 

Let get started from the beginning.

So What is the Difference Between PCIe x1 vs x16?

As clarified earlier, the essential difference between x16 vs x1 is that the former has 16 PCIe data lanes and the later has a single PCIe data lane.

However, in order to truly  grasp the differences between PCIe x16 and x1 in detail, you need to understand some core principles of the PCIe interface.

Basically, the core principles you need to understand are:

  1. PCIe protocol comprises of PCIe lanes.
  2. Higher the number of PCIe lanes, higher the transfer speed of the slot or the bandwidth requirement of the expansion device.
  3. Additionally, PCIe lanes conform to different versions which has a huge impact on per lane performance 
  4. The PCIe protocol is cross, backward and forward compatible.

What is the PCIe Interface and PCIe lanes?

PCIe interface is one of two primary interfaces, the other one being SATA, that is used to connect various components to your PC. 

This can include a graphics card, a WiFi Card, Video Capture Card etc. All of these various components add different functionality to your PC and they require a PCIe slot.

Now the PCIe interface comprises of PCIe lanes. You can think of these as information highways. The number of PCIe lanes each PC has are limited and are determined by your motherboard and your CPU.

Also Read: How Many PCIe Lanes Do I Have? 

The number of PCIe lanes a certain component needs to function optimally varies.

For instance, a WiFi Card can work optimally with just a single PCIe lane. Whereas a graphics card needs 16 lanes to work optimally.

The following tables lists various devices and the number of PCIe lanes they require.

CardPCIe Lane
Requirement
Remarks
NVIDIA Graphics Card16 or 816 ideally
8 in case of SLI
AMD Graphics Card16, 8, or 416 ideally
8 or 4 in case of crossfire
Sounds Card1
Ethernet Network Card1 or 41 in case of 1 Gbps (v3.0)
4 in case of 10 Gbps (v3.0)
WiFi Network Card1
Video Capture Card1 or 41 in case of 1080 capture (v3.0)
4 in case of 4k capture (v3.0)
SATA Expansion and
Raid Controller
1, 4, 8The lane requirement depends upon number of SATA slots, and whether it has RAID Controller
M.2 NVMe Expansion Card4
TV Tuner Cards1
Port Expansion Card1 or 4Depending upon the type and number of port. Thunderbolt 3.0 port, for instance, requires 4 PCIe Lanes (v3.0)
Riser/Splitter1, 4, 8, 16

Read in Detail: What are PCIe Lanes?

There are basically four types of PCIe slots differentiated by their physical size and lane count.

  • x1 slots: These are the smallest and have only a single PCIe lane
  • x4 slots: These have 4 PCIe lanes and intended for moderately demanding expansion cards. x4 slots are rare.
  • x16(x4) slots: These slots have the physical dimensions of a full x16 slot but are hardwired to only four physical lanes (they have the throughput rate equivalent to an x4 slot).
  • x16(x8) slots: These also have the dimensions of an x16 slot but have 8 PCIe lanes. 
  • x16 slots: A True x16 slot offers full 16 lanes. As such, these slots have the highest throughout rate and are intended for the most demanding expansion cards such as graphics cards.

The following table shows the throughput rate of different PCIe slots and their versions.

Versionx1
(GB/s)
x2
(GB/s)
x4
(GB/s)
x8
(GB/s)
x16
(GB/s)
1.00.2500.500 1.0002.0004.000
2.00.5001.0002.0004.0008.000
3.00.9851.9693.9387.87715.754
4.01.9693.9387.87715.75431.508
5.03.9387.87715.75431.50863.015
6.07.87715.75431.50863.015126.031

So an x1 slot conforming to PCIe 4.0 has a throughput rate of 1.969 GB/s. A true x16 slot conforming to PCIe 4.0 has a throughput rate of 16 times as much i.e 31.508 GB/s.

The Higher the Number of PCIe Lanes; The Higher The Bandwidth

A rule of thumb to note is that the throughput rate (transfer speed in layman’s term) of a slot or a PCIe device is determined by its lane count.

Basically, the transfer speed scales with the number of PCIe lanes. So an x4 slot has four times the throughput rate as compared to an x1 slot. 

An x16 slot in turn has four times the throughput rate as compared to an x4 slot.

What this means in the end, is that an x16 slot can handle much more demanding expansion cards as compared to an x1 slot. 

Point to Note: The PCIe Version Matters

A very critical side note here is that the PCIe version of your motherboard and of your device matters a ton.

This is because with each newer version of PCIe, the transfer speed per lane doubles! This in turn means that newer PCIe interfaces can handle much more demanding expansion cards as compared to older versions.

You can see from the table above that a PCIe 3.0 x1 slot has a transfer speed of 0.985 GB/s. The same slot if conforming to PCIe 4.0 has a transfer speed of twice as much at 1.969 GB/s.

Newer versions of the slots means your system would be able to support newer PCIe devices at their optimal performance.

Take for instance the PCIe 4.0 NVMe SSD Samsung 980 Pro. In order to make it work at optimal speeds, the M.2 slot needs to conform to V4.0 as well. If you plug this into V3.0 M.2 slot, it will work at half the speed! 

samsung 980 pro
Samsung 980 Pro. M.2 PCIe 4.0 NVMe SSD

Main Differences Between PCIe x1 and x16

With the introduction out of the way, let us get to topic in hand. 

Generally, the number AFTER the “x” denotes the number of PCIe lanes. 

So for instance, an x1 slot connects to a single PCIe lane whereas an x16 slot has 16 lanes IDEALLY (but not always; read on).

What Does PCIe x1 Mean?

So as explained earlier, a PCIe x1 slot is a slot that only connects to a single PCIe lane.

x1 slot pcie
A PCIe x1 slot is the smallest PCIe slot on a motherboard

This is the smallest PCIe slot on a motherboard and since it connects to only a single PCIe lane, it is only suitable for low demanding devices.

So an x1 slot is suitable for devices like:

  • Sound Cards
  • Ethernet Network Cards
  • WiFi Card
  • HD Video Capture Card
  • SATA Expansion Card
  • TV Tuner Cards
  • Port Expansion Card
  • Riser/Splitter

As such, an x1 slot is the weakest in terms of the overall throughput rate it can support.

A WiFi card shown below is one of the most common expansion card intended for the x1 slots. Pay attention to its x1 connector.

Tp Link WiFi Card
A WiFi Card with an x1 connector

Also Read: What Are PCIe x1 Slots Used For?

What Does PCIe x16 Mean?

PCIe x16 slots are perhaps the most confusing to understand. 

An x16 slot is the largest slot on a given motherboard.

Difference Between PCIe x1 and x16
x16 Slots are the largest PCie slots on a motherboard

The biggest use of an x16 slot is for plugging in the graphics cards. Graphics cards are large and have an x16 connector. They ideally require 16 lanes to work at optimal performance.

Graphics Card
Graphics card plugged into an x16 slot

However, the number “16” after the “x” in this case DOES NOT ALWAYS refer to the number of lanes the slot offers.

Take for instance the PCIe slot of the following motherboard (Gigabyte GA-P67A-UD3), you can see that this motherboard has two PCIe x16 slots (colored in blue), HOWEVER, while the second one on the bottom has the full size of an x16 slot, it only offers 4 lanes!

Difference Between PCIe x1 vs x16
 The motherboard above has three x1 slots and two x16 slots (one x16 slot working in x4 mode).

As such, an x16 slot can be found in three different lane configurations:

  • Full x16 slots: These slots offer the full 16 lanes. These are ideal for graphics cards. All commercial motherboards have at least one x16 slot with full 16 lanes.
  • x16(x8) slots: These slots offer 8 lanes. These often used for dual graphics card setup. A graphics card CAN work with 8 lanes.
  • x16(x4) slots: These slots are NOT intended for a graphics cards. Instead, these are used for lower demanding devices like an NVMe expansion card, 4K video capture card etc.

It should be noted that while you cannot plug an x16 card into an x1 slot, you CAN plug an x1 card into an x16 slot and it will work just finehowever, in doing so you would  waste the potential of the larger more powerful x16 slot.

Also Read:

Summary: PCIe x1 vs x16

x1

  • An x1 slot is the smallest PCIe slot on a motherboard. 
  • x1 slot connects to only a single PCIe lane
  • An x1 slot can only be used with PCIe device that have an x1 connector like a WiFi Card or a Sound Card.

x16 

  • An x16 slot is the largest PCIe slot on a motherboard
  • An x16 slot can connect to 16, 8 or 4 PCIe lanes
  • Generally, a motherboard has ATLEAST ONE x16 slot with full 16 lanesand it is usually the first one.
  • x16 slot is often used for the graphics cards or other large and demanding PCIe devices
  • x16 slot can be used with devices with smaller connectors such an x8, x4, or even x1 device. 
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Author:

Atif Qazi
Atif Qazi is the founder of PCGuide101. He is a digital nomad who loves everything PC. He is a PC builder, tech enthusiast, engineer, and a lover of single player lore-rich RPG games.

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