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Will PCIe Work in PCI Slot? – Learn Here

Ever since people started extending the functionality of their computers, standards have been implemented to ensure that the process is handled efficiently and that the computers can function properly with the new peripherals.

Among the many standards, two stand out because they are popular and can be a little confusing, especially because they almost share a name. PCI (Peripheral Component Interconnect) and PCIe (Peripheral Component Interconnect Express) have been around for many years. PCIe was unveiled in the early 2000s whereas PCI has been in use for even longer.

While these slots perform more or less the same functions, they are quite different in terms of performance and even physical profile. So you may be asking, will PCIe work in PCI slot?

There’s a lot we need to consider with this but generally, NO! these two standards are not hardware-compatible. More on this as we go along.

The PCI Standard

This older standard was introduced as a way of unifying the type of slots that were used to add peripherals to older computers. The PCI slot is capable of taking on all manner of expansion cards that are compatible with it and work just fine.

It has even be referred to as a ‘plug-and-play’ expansion option because the amount of configuration needed to get it to work is very minimal.

Once the card is installed, the computer can go about determining what resources the card needs and it ‘figures’ out how to supply those resources.

The standard was invented in the 1990s by Intel and it was initially used in servers. However, much later the standard was adopted into personal computers, and ever since then, it can be found on many motherboards, sometimes even alongside the newer PCIe slots.

PCI Slots on a motherboard
PCI Slots were used on motherboards to connect additional peripheral devices. Source: techyv.com

Devices that Use the PCI Slot

The PCI computer bus is used to attach peripheral devices to a motherboard, letting you customize your computer with features that are supported by the accompanying PCI cards.

Many PCI expansion cards used to add features to the motherboard have their PCIe equivalents for those with new non-PCI motherboards. Nevertheless, some of the devices that are supported by the PCI standard include the following:

A network card is a piece of hardware (also known as a Network Interface Card) that lets your computer connect to a network.

It is an integral piece of a computer and if yours doesn’t have a functioning NIC or the one you have doesn’t meet your requirements, the PCI slot can let you add another one.

You can also add a video card that can be used instead of the computer’s integrated graphics to get better performance in applications like games.

A PCI sound card will let your PC process sound better and even fine-tune the audio output to your liking while a wireless adapter can add wireless connectivity like Wi-Fi and Bluetooth to your computer.

Also Read: What PCIe Slot do I Have?

Advantages and Disadvantages of PCI

PCI enabled multiple peripheral devices to share the same standard slot and connect to the computer. This allowed users to install whichever devices they needed on a pc and not run the risk of incompatibilities.

Furthermore, the PCI standard enabled faster communication during the late 90s and early 2000s when it was greatly in use. Computers weren’t that fast then but the speeds that PCI allowed were just sufficient. It allowed users to transfer data at up to about 500 MB/s which was remarkable at the time.

With computer improvements, the PCI standard started to become too slow for the demands that new computers had. This paved way for the invention of the PCIe standard.

So as a disadvantage, PCI was significantly slower than PCIe and hence it was replaced by the latter.

Also Read: PCIe 3.0 vs 2.0

The PCIe Standard

PCI-SIG is the community that ensures these standards are well developed and maintained. As PCI became slower, PCIe came in and took the reins with the first-ever PCIe generation hitting the mainstream markets about a year after the standard was introduced.

Most computers today make use of the PCIe standard because it has proven to be effective with handling large amounts of data being transferred between the components and the CPU.

PCIe has been evolving and with each new version released, the speed has almost been doubling. This has allowed manufacturers to create faster components like gigabit network cards and graphics cards that can handle the large bandwidths.

While the current most available PCIe generation is the PCIe 3.0, some PCIe 4.0 – ready motherboards are already available and support speeds of up to 64GB/s in an X16 slot. The PCIe 5.0 and 6.0 standards are also in the mills.

Devices that use the PCIe slot are the same kind as those that use the PCI slot. You have video cards, sound cards, etc.

PCIe Slots on a motherboard
PCIe Slots like the ones pictured above are much faster than the older PCI slots. Source: deskdecode.com


PCI is a parallel interface standard that connects devices through a PCI bus to the motherboard. On the other hand, the PCIe standard describes a serial connection where each slot has lanes that transmit data individually to the CPU. They don’t use a common data bus.

PCIe is also much faster than PCI as it allows speeds of between 250 MB/s up to 64GB/s whereas PCI can do a high of 532 MB/s for a 64-bit connection operating at 66MHz.

With speed alone in consideration, we see why PCIe replaced PCI. Many modern devices, including some SSDs, exceed the speed limits that the PCI interface could offer.

Lastly, PCI cannot support as many devices as PCIe can. With PCIe, you can connect up to 32 devices if your computer supports them, although the higher slot numbers are typically in the realm of server-grade computers.

Regardless, standard PCI slots with their bus architecture can only support about five devices.

Also Read: How to Update Motherboard Drivers?

Will PCIe Work in PCI Slot?

Seeing that the PCI and PCIe standards are two very different implementations of the same technology, it’s easy to tell that a PCIe device will not work in a PCI slot for a few different reasons.

First, the two slots are different in terms of notch placements. The notches are used to restrict the use of different volt PCI cards (5 volts and 3.3 volts) on a single slot. However, a PCIe card slot has a ridge that’s placed differently from a PCI slot so the card won’t fit.

Another issue that causes incompatibilities is the architecture that’s used. Where PCI uses a parallel bus-based system, PCIe slots make more use of a serial connection instead.

Both slots are also wired up differently such that using a PCIe card on a PCI slot would be impossible.

Will PCIe Work in PCI Slot?
PCI slots come in either 32-bit or 64-bit form depending on the motherboard. Source: partitionwizard.com

However, some modern motherboards do still offer PCI slot for legacy support. They have a dedicated chipset that makes a PCIe motherboard support PCI slot.

Asus Prime B350 Plus
Asus Prime B350 Plus is an example of newer motherboard that has legacy PCI slots. Source: ASUS


We have demystified one of the many confusing things about computer peripherals. The different standards are meant to do the same thing but they don’t work the same. One is a worthy replacement of the other and as the years have passed, it has proven that it’s still quite useful.

Tackling the question, will PCIe work in the PCI slot has yielded a lot of information which alludes that these two standards should never be mixed.

Because of the differences in wiring and connection methods, forcing a device into a slot that isn’t meant for it can result in damages.

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