What Is PCI Slot | an Overview of Global Hardware Connectors

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With the improvement and changes of computer motherboard over the past few decades, many forms and versions of connectors have been released to perfectly suit the need for connectivity along with major improvements in reliability and data transfer. The PCI slot is one of the most influential of these. In this article, we’re going to discuss what is PCI slot, and a general overview of its introduction and usage.

What Is PCI Slot

What is PCI Slot

An Overview

PCI, also known as Peripheral Component Interconnect, is a slot used mainly in devices like computer motherboards, in order to connect to various hardware to the motherboard. These are manufactured by Intel. Adding PCI slots is an easy way to add more expansion cards into the motherboard. It’s a popular computer bus slot that fits almost all major hardware components like modems, network and sound cards, etc. PCI slots come with 32-bit or 64-bit width. PCIe is the most used upgraded version of PCI slots.

An Overview

The bus is a system where data transfer can occur between various components. It can be within one device or between multiple devices at once. The PCI slot is a form of bus system which also complies with PCI local bus standards. To upgrade a computer beyond the limit of the motherboard’s holding capacity, PCI slots are a popular method to go for. To learn how many slots you have, you can easily check the motherboard and upgrade them.

How to Use

Although PCI slots have mostly been replaced with PCI-e slots, they were very popular in the early computers. We can rarely see them now, in aged motherboards. Using a PCI slot is very easy, as the process is the same for all instances. You can find these PCI slots easily by looking for long buses (usually white, rail line-shaped) in the motherboard. PCI and PCIe slots can coexist on the same motherboards. In that case, PCIe slots will be of a different color, shorter in width, and longer in length.

How to Use

Motherboards contain a limited number of PCI lanes which can’t be increased without upgrading the motherboard itself. But these PCI lanes can be utilized. You can add hardware components to these lanes. Look for the PCI bus in hardware, which is a long straight line of connectors with usually a golden color.

Keep in mind that the connector must be PCI compatible, otherwise, you won’t be able to attach the hardware in your motherboard. If it’s compatible, place the connector inside one of the lanes in your motherboard. PCI comes with one or more notches, so place them at the correct order. Afterward, it should be attached firmly and tightly in the slot and will be ready to use.

Different Versions of PCI Interface

Over the years, PCI has seen many upgrades to fit the need for bandwidth and power consumption. There are generic versions, along with universal and extended versions which are backward compatible (can be used in previous version slots) to normal PCI. PCI slots work on parallel interface method, where it divides a large amount of data into small groups, and then transfer them.

Different Versions of PCI Interface

These interfaces have 32-bit and 63-bit bus widths, with different notch positions to make them unique to their counterparts. PCI made its journey with the PC-XT and PC-AT slots that were used a long time ago. They were generally named as ISA (Industry Standard Architecture).

Different Versions of PCI Interface a
  • PCI 1.0 came out in the 90s, primarily in 32-bit with 1 notch. It had 5V signaling with a data transfer rate of up to 133MB/s.
  • PCI 2.0 boasted 3.3V slots. These aren’t backward compatible with PCI 1.0. The notch position was flipped to prevent accidental connection to previous slots.
  • PCI 2.1 had major upgrades over previous ones as it had 66MHz support for 32-bit and 33MHz for 64-bit ones. The transfer rate was twice the previous ones, 266MB/s.
  • PCI 2.2 is also known as “Mini PCI” because it is intended for laptop connectors. It had 32-bit 3.3V and 33MHz bus clock.
  • PCI-X (PCI-Extended) was built for server purposes, and it was backward compatible with previous PCIs. It boasted a whopping 1064MB/s at 133MHz clock.
Different Versions of PCI Interface b

There were many more versions for multipurpose applications. A specialized PCI version was used as AGP (Accelerated Graphics Port) slots dedicated for video cards.

Different Versions of PCI Interface c

Practical Applications and Advantages

The reason PCI interfaces gained so much popularity back then is because of its versatile hardware support and high data transfer rates. Virtually any hardware component was compatible with the PCI interface. Alongside compatibility, additional advantages were also found.

Hardware that utilized PCI cards is sound cards, internet modems, extra USB ports, TV cards, ethernet and Bluetooth connectors, etc. When the existing USB ports were filled, external ones could be attached to the motherboard via PCI.

Another great example is connecting the SSD (Solid-state drive), which is a high-speed storage device compared to hard discs. SSD can be connected via PCI using the NVM (Non-Volatile Memory) technology, which superseded the performance of traditional SATA interface connections. AGP slots are another form of PCI dedicated to graphics cards. AGP and AGP pro slots were used before PCI-e technology came along.

Practical Applications and Advantages
Practical Applications and Advantages a

Disadvantages of PCI

Although PCI boasted the performance and reliability for a long time, it is almost useless nowadays because of its upgraded version, PCI-e. For this, PCI slots are very rare today and can be seen in only the old computers. The data transfer rate is also much lower than modern standards.

Most of the PCI versions are neither forward nor backward compatible, which makes them obsolete when a newer version comes out. And although PCI can be used to increase utilization by adding hardware components, the slots themselves can’t be increased. These slots are permanent on a motherboard, and upgrading them is only possible by buying newer motherboards.


In this article, we’ve briefly covered an overview of what is PCI slot. Although being absent in modern days, the PCI slot was the pinnacle among all other hardware connectivity methods and shaped much of today’s wide compatibility among devices. In that aspect, it’s a significantly important technology.

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