Difference Between PCI and PCI Express (With Table)

These days the usage of connecting slots have become very common. An expansion slot, otherwise referred to as a bus slot or expansion port, is a port or hardware connecting space located on the motherboard of computer systems. They allow expansion cards to be connected to a computer system.

Upgrading a motherboard can solve the issues of incompatibility in a system, if any. But for the upgrade to take place, the types of slots present on the motherboard should be known along with their replacement needs, i.e., whether a particular slot fits a particular replacement part.

Nowadays, things have changed, every individual has a different choice or need when it comes to technological advances. Keeping this in mind, there are various types of expansion slots present today. PCI, PCI Express, AGP, ISA, AMR, CNR, EISA and VESA are the ones.

PCI vs PCI Express

The difference between PCI and PCI Express is that PCI Express is faster than PCI and uses a serial interface, whereas PCI on the other hand, uses an interface that is parallel and older.

Comparison Table Between PCI and PCI Express

Parameter of ComparisonPCIPCI Express
OriginIntroduced in 1992 by Intel. Introduced in 2003 by Intel, Dell, HP and IBM.
ConnectionOnly connects hardware devices and graphics cards. Whereas, it connects WiFi, graphic ports and others.
SpeedSlower as compared to PCI Express.It is faster.
Data rateSlower data rate.Faster data rate.
Slot typeStandardized slots are present. Slots depending upon the number of lanes are present.
Bandwidth133 MB/s with 33 MHz, 206 MB/s with 66 MHz and 532 MB/s with 66 MHz.Varies from 250 MB/s to several GB/s.
FeaturesIt has a very limited amount of features. It has more developed features than PCI.
Hot pluggingNot supported or optional.Supported.

What is PCI?

Peripheral Component Interconnect, or PCI is an expansion slot in a computer system used for connecting hardware devices to the system. Originally introduced by Intel in 1992, PCI is the most commonly used expansion slot till date.

Otherwise known as Conventional PCI, it works on a parallel interface having a single bus standard. Devices that are connected to the PCI bus are first connected to their respective buses and then, they are allotted addresses.

PCI is either of 32-bit or 64-bit in width, the latter being created after a few years. There are preferably three types of PCI bus that are used in common, i.e., PCI with 32-bit and 5V signal voltage, PCI with 64-bit and 5V signal voltage, and PCI with 64-bit and 3.3V signal voltage. The connection is done through a list of steps, i.e., receiving, supplying, sensing and then providing the PCI card.

Moreover, the original PCI does not actually need a hot-swappable bus, so the system power should be turned off whenever any card is inserted into or removed from the PCI slot.

What is PCI Express?

Peripheral Component Interconnect Express, or PCI Express, officially known as PCI-e, is a high-speed expansion slot used for connecting hardware devices and many more in a computer system. PCIe was first introduced by Intel, Dell, HP and IBM in 2003 to replace the PCI and bring improved changes.

Most commonly used in the expansion of laptop cards and computer storage, the PCIe comes with a serial interface. The current generations of PCIe are PCIe 1.0, PCIe 2.0, PCIe 3.0 and PCIe 4.0. The bandwidth of PCIe being 1 GB/s for each lane, tends to be doubled with each generation.

PCIe turned out to be more compatible with the existing operating systems than PCI and is considered to be a better version, undoubtedly. The connection involves installing, connecting and transmitting the PCIe interface card.

A DMA (Direct Memory Access) engine is compatible with the PCIe and as a result, provides better performance and low-occupancy, if the commercial solutions are unable to solve any problem.

Main Differences Between PCI and PCI Express

  1. PCI has an older parallel interface, whereas PCIe has a serial interface.
  1. PCI was introduced first in 1992, and PCI was introduced 11 years later in 2003.
  2. PCI is able to connect hardware devices, graphic cards, modems etc. while PCI can connect WiFi too.
  3. PCI is slower as compared to PCIe and it even has a slower data rate.
  4. There are standardized slots present in PCI, while in PCIe the slots depend upon the number of lanes present.
  5. Bandwidth in PCI is 133 MB/s, 206 MB/s and 532 MB/s. But in PCIe, it varies from 250 MB/s to several GB/s.
  6. Being the older version, PCI contains a very limited amount of features. PCIe being the updated one, has more developed features.
  7. The feature of hot plugging is supported only in PCIe and is optional in PCI.

Conclusion

To be specific, PCI and PCI Express are quite different in their type, function as well as bandwidth. The PCIe being the replacement of PCI, is faster and more compatible. Still, many devices use PCI slots even today due to its simpler interface and also because every device does not really need the speed advantage in it.

Upgrading a computer system’s expansion slot ensures a drastic change in it. May it be PCI or PCIe, both of these help in the connection of cards and devices in a wide range. Although PCI and PCIe slots are not compatible with each other, they have different configurations. However, most motherboards have a combination of both these slots. Such motherboards comprise of a PCB (Printed Circuit Board) expansion card, a PCI slot, two connectors and a PCIe slot. The PCI and the PCIe slots are already in electrical contacts, i.e., PCI slot has a PCI card fitted into it and PCIe slot has a PCIe card fitted into it.

PCIe allows each lane to have its own bandwidth, which in turn solves the problem of interference of lanes. But, as the world keeps changing, there might soon be a more developed version of PCIe created with better features and functions.

References

  1. https://scholar.google.com/scholar?as_vis=1&q=pci+slot&hl=en&as_sdt=1,5#d=gs_qabs&u=%23p%3DCdOBznbN4dUJ
  2. https://ieeexplore.ieee.org/abstract/document/7111377