The amount of PCIe slots you needs depends upon how many PCIe expansion cards you wish to install. A motherboard can have anywhere between a single PCIe slot, all the way upto 6 or 7 seven slots in varying configuration and sizes.
So the answer to the question, how many PCIe slots do I need depends upon what kind of PC you intend to build. A gaming PC, for instance, may require nothing more than a single PCIe x16 slot for the graphics card.
Others may require multiple PCIe slots for installing multiple graphics cards, WiFi card, video capture card, dedicated sound card, port expansion cards etc.
In order to figure out how many PCIe slots you actually need, it is better to first talk about all the different PCIe devices that you can plug into PCIe slots.
PCIe Devices and Their Slot Requirement
There are many PCIe devices out there that you can install. These include: graphics cards, WiFi card, ethernet card, sound card, port expansion cards etc.
The following table shows all the devices that you can install on PCIe slots as well as the type of slot they need.
| Card | PCIe Lane Requirement | Remarks |
|---|---|---|
| NVIDIA Graphics Card | 16 or 8 | 16 ideally 8 in case of SLI |
| AMD Graphics Card | 16, 8, or 4 | 16 ideally 8 or 4 in case of crossfire |
| Sounds Card | 1 | |
| Ethernet Network Card | 1 or 4 | 1 in case of 1 Gbps (v3.0) 4 in case of 10 Gbps (v3.0) |
| WiFi Network Card | 1 | |
| Video Capture Card | 1 or 4 | 1 in case of 1080 capture (v3.0) 4 in case of 4k capture (v3.0) |
| SATA Expansion and Raid Controller | 1, 4, 8 | The lane requirement depends upon number of SATA slots, and whether it has RAID Controller |
| M.2 NVMe Expansion Card | 4 | |
| TV Tuner Cards | 1 | |
| Port Expansion Card | 1 or 4 | Depending upon the type and number of port. Thunderbolt 3.0 port, for instance, requires 4 PCIe Lanes (v3.0) |
| Riser/Splitter | 1, 4, 8, 16 |
So here you can see that a graphics card ideally requires an x16 slot. A WiFi card requires an x1 slot etc.
This brings us to the next point.
The Type of PCIe Slots
PCIe slots can be found in varying configuration. They are differentiated by two aspects:
- Their physical size
- The amount of PCIe lanes they connect to
As far as the physical size is concerned, PCIe slots are found in two sizes on a typical commercial motherboards, x1 size and x16 size.
As far as the PCIe lanes are concerned, that is another story particularly with the x16 slot.
While an x1 slot has one PCIe lane, an x16 slot can have 16, 8 or even 4 PCIe lanes.
A high demanding expansion card such as a graphics card requires a true x16 slot ideally – or an x16 slot with fill 16 lanes.
Generally, the top or the first x16 slot on a given motherboard offers the full x16 lanes.
Here are some article for more details:
Understanding what PCIe lanes are is a great concept for PC builders. PCIe lanes are basically channels that carry information to and from the PCIe slots and the CPU.
The amount of information a slot can carry scales with the amount of PCIe lanes it has. Therefore, a PCIe slot with 4 lanes can carry four times as much data s compared to a slot with one PCIe lane.
The higher the amount of lanes a slot has, the more powerful device it can be occupied with.
The Amount of PCIe Slots Varies With Motherboard
Not all motherboards have a standard amount of PCIe slots.
The amount of PCIe slot varies greatly depending upon what chipset the motherboard features as well as its form factors.
Motherboard Form Factor and Amount of PCIe Slots
The motherboard form factors, or its size, greatly affects the amount of PCIe slots it can have.
There are three common motherboard sizes for commercial PCs and one for workstation (EATX).
The following table explains the purpose, size as well as the amount of PCIe slots you can expect from different form factors.
| Form Factor | Dimensions | Purpose | Remarks | No. PCIe Slots |
|---|---|---|---|---|
| ATX (aka Full-ATX Standard ATX) | 12 x 9.6 inches 305 x 244 mm | Commercial | - For Gamers and Professional - Fairly common - Best expansion capability for commercial purpose | 2-3 x16 2-3 x1 |
| Micro ATX (aka mATX) | 9.6 x 9.6 inches 244 x 244 mm | Commercial | - Feature affordable motherboards - Moderate expansion capacity | 1-2 x16 1-2 x1 |
| Mini ITX | 6.7 x 6.7 inches 170 x 170 mm | Commercial | - Smallest motherboards or PC - Minimal expansion capacity - Expensive due to their compact design | 1 x16 |
| Extended ATX (aka E-ATX) | 12 x 13 inches 305 x 330 mm | Workstation | - Intended for workstation builds - Expensive and compatible only with specialized workstation CPUs. | 4-7 x16 |
Slot on ATX Motherboards
ATX is the largest and the most common form factor for commercial PCs. Motherboards with this form factor can feature two to three x16 slots along with a few x1 slots.
ATX motherboard is considered the most expandable for commercial PCs. You can install multiple graphics cards, and still have plenty of slots to plug in your WiFi, video capture card etc.
Slot on Mini ITX Motherboards
Mini ITX motherboards, on the other hand, are considered the least expandable. They ONLY feature a single x16 slot which in most cases is used by the graphics card.
These motherboards often have WiFi Built-in so you don’t need to worry about having an x1 slot for adding in an additional WiFi card here.
But other than that, there is nothing more you can do. For instance, if you are a streamer, you will have no place to plug in the video capture card here.
Also Read: How to Check Form Factor of Motherboard?
Chipset and The Amount of PCIe Slots
Another important determining factor for the amount of slots your motherboard can have is the chipset it features.
Different motherboard chipsets feature different amount of PCIe lanes. The more PCIe lanes a chipset offers, the more slots it can have.
Low-end motherboard chipsets such as the AMD A or the Intel B series chipset often have a low amount of PCIe lanes and hence, they do not have a high amount of PCIe slots.
AMD X and Intel Z series motherboards, on the other hand, feature a high amount of PCIe lanes and thus a higher number of PCIe slots.
Also Read: Can a PCIe 4.0 Device Work in a PCIe 3.0 Slot?
So How Many PCIe Slots Do I Need?
Again, the answer to that question depends upon your needs.
If Building a Robust Gaming and Streaming Setup
When building a robust gaming PC whereby you plan to install a graphics card, a WiFi card, a video capture card and perhaps a dedicated sound card, you would need:
- x16 slot for graphics card
- x1 slot for WiFi card
- x1 slot for sound card
- x4 slot for 4k video capture card
If you plan to add two graphics cards, then you would need two x16 slots (x16 slot with at least x8 lanes).
You would obviously need an ATX motherboard here as they offer a high amount of PCIe slots.
If Building an Average Gaming PC
For an average gaming PC, you don’t really need much. You could have:
- x16 slot for graphics card
- x1 slot for WiFi card
You may need one more x1 slot in case if you want to add a dedicated sound card or a USB expansion card.
If Building a Compact PC
For instance, if you are a gamer or someone planning on building a compact PC with Mini ITX motherboard, then the single x16 slot it provides should suffice.
You could use the single x16 slot for the graphics card and practically, you wouldn’t really need much more than this.
Additional Add-in Card Would Require More Slots
So for specialized needs such as when installing an additional USB, M.2 or SATA expansion cards, or when installing a TV tuner card, you would need more slots.
Again the table in the article above highlights different cards and their corresponding slot requirement.
Being Mindful of the Graphics Card Size
When deciding on how many PCIe slot do you need, you have to take into consideration the fact that certain PCIe devices are large and can take up the space of more than one slot.
Take for instance, the following graphics card inserted into an x16 slot.
You can see that of the three x1 slots on this motherboard, two of them are entirely blocked by this graphics. Only one is available for use (top).
There are typically three sizes of graphics card:
- Low Profile: 1 and 1.5 slot
- Average: 2 and 2.5 slot
- Large: 2.7 and 3.0 slot
You can figure out the size of the GPUs before purchasing by looking at its specsheet.
Hence, when building a PC and when deciding on the amount of slots you need, you need to take the size of expansion cards into consideration as well.
Final Words
The answer to the question how many PCIe slots do I need all depends upon your needs or the amount of expansion cards you wish to install on your PC.
You may not need any PCIe slot at all! If you have an average PC for home and office use, then you may not need PCIe slots at all.
While all PC motherboards do have at least one PCIe slot, for simple builds, you may not have the need to use any PCIe slot at all.
For simple home and office builds, the built-in features, such as the integrated CPU graphics card, built-in WiFi etc should suffice.
