An Overview of PCI (Peripheral Component Interconnect) Slot [MiniTool Wiki]

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What Is PCI Slot

PCI (Peripheral Component Interconnect) is an old local computer bus, which is used for attaching hardware devices within a computer. The PCI is also a part of the PCI bus standard. Further detailed information about PCI slot will be introduced in this post of MiniTool.

The PCI bus supports the functions that are found on the processor bus with a standardized format that is different from any specific processor’s native bus. The PCI slot is an embedded slot on a device, which allow you attach to the various hardware components including network cards, sound cards, disk controllers and other kinds of peripherals. These devices can be called PCI devices.

The PCI slot usually is used as a component of conventional do-it-yourself desktop computer. Hence, PCI is also referred to as conventional PCI. With the occurrence of the successor PCI Express, PCI slot gradually get obsolete. Even so, it is still in use.

Main PCI Slot Types

Here are 3 main available PCI slots (64-bit PCI, 32-bit PCI and PCI-X and PCI Express (PCI-E)) on the market. They look different and accept different devices as well. Putting a PCI card in the wrong slot can do harm to the card and possibly run the entire computer.

64-bit PCI

Some manufactures have stopped producing any products compatible with this 64-bit PCI slot. It is not commonly utilized now. But all the G4 and G3 Macintosh computers used it. Hence, these devices can be referred to as PCI computer. This 64-bit PCI slot can be recognized by its three segments. And the shortest segment is located in the center.

32-bit PCI and PCI-X

Several expansion cards produced by LaCie use this 32-bit PCI and PCI-X. The medium-length slot on the left side is the main difference between the normal 32-bit PCI slot and PCI-X. It is markable that only PCI-X has this final segment.

The 32-bit PCI cards can work properly in a PCI-X slot, while PCI-X card is unable to work in a standard 32-bit PCI slot. Generally speaking, all PC motherboards at least have the 32-bit PCI slot. Macintosh G5 used PCI-X until the new version – liquid-cooled hardware comes into being.

These slots can be distinguished from the 64-bit PCI via the organization of the segments. The small segment is located at the start instead of the center.

PCI Express (PCI-E)

Computers produced after 2005 nearly came with PCIe slots. As the length of this slot is various, it is difficult to identify. And these variations are referred to as lanes. Besides, they are called 1x, 8x, 16x and something like these based on the length.

Tip: All connectors on a PCIe slot are obviously smaller and they are set farther into the motherboard instead of PCI slots.

A 1x PCI slot usually begins with the same small segment, but is followed by a second small segment. It seems that the more lanes you have the faster interface speed you will get. For most PCIe cards, they are 1x or 4x.

The 1x PCIe expansion card can fit into the 16x slot. Due to different physical size, a part of slot space will be unoccupied. This is a normal and you don’t have to worry about it.

Note: To know the difference between the PCI and PCIe, you can refer to this article: PCI vs PCIe: What’s the Difference and How to Distinguish Them?

The Evolution of PCI

PCI has a long history. In this development process, there are several main PCI generations.

  • PCI 1.0 (1992): This one has both 32-bit and 64-bit versions.
  • PCI 2.0 (1993): It comes with two notches, so it is easy to differentiate 3.3V and 5V slots.
  • PCI 2.1 (1995): The change on this version is the improvement of clock speed.
  • PCI 2.2 (1998): It boosts the readability of the slots and incorporates ECNs.
  • PCI 2.3 (2002): It deletes the 5V keyed add-in cards.
  • PCI 3.0 (2004): It out-performs all the previous versions and completely removed support for 5V keyed system board connector.

Bottom Line

Read here, you may have an overall understanding of PCI slot including its definition, usage, main types as well as development history. Here comes the end of this post.

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