What PCI vs PCI Express Signify
Introducing PCI
PCI, also known as peripheral component interface, is a connectivity interface standard established by Intel in 1990. Initially used solely in servers, PCI became prevalent in computers and other network devices, such as network switches, from 1995 to 2005. Typically, PCI is inserted as an optional feature into a PCI slot on a motherboard. Well-known PCI extension cards include NIC cards (network interface cards), graphics cards, and sound cards.
The original 32-bit, 33MHz PCI interface achieved data transmission rates of 133Mbps. The updated 64-bit, 66MHz standard allowed for greater data transfer rates at frequencies up to 533 MHz. In 1998, IBM, HP, and Compaq introduced PCI-X, which expanded the data transfer rate to 1064MHz while maintaining full compatibility with PCI.
Exploring PCI Express
PCI Express, or PCIe, is the successor to PCI and was developed by Intel in 2001 as a more advanced connectivity standard. It offers higher bandwidth and improved compatibility with modern computer systems compared to PCI. Similar to PCI, PCIe can be used for various circuit boards, such as PCIe Ethernet cards, that are inserted into a PCI Express slot.
PCI Express comes in configurations of x1, x4, x8, and x16, all of which increase bandwidth by the same factor. Larger deployments require longer PCI Express slots, with the x16 slot being the largest and the x1 slot being the smallest. PCIe cards can be inserted into any slot size that can accommodate them, such as placing an x4 card into an x8 slot but not into an x1 slot. The primary advantage of PCI Express is its ability to facilitate high-speed data transmission, making it suitable for linking peripherals like high-end video cards and Gigabit Ethernet cards. Furthermore, PCI Express is fully compatible with both PCI software and hardware.
The Distinctions Between PCI and PCI Express
PCI Express, as the successor to PCI, differs from its predecessor in several ways, including operating topology and bandwidth. Here, we present a basic comparison between PCI and PCI Express.
In terms of working technology, PCI operates as a bus, with devices connected to the PCI bus acting as bus masters, allowing them to connect directly to their own bus. Conversely, a PCIe card functions as a high-speed digital connection. PCIe implements a switch that controls multiple point-to-point serial connections instead of a single bus that manages data from multiple sources.
Regarding bandwidth, PCI has fixed lengths for its 32-bit and 64-bit variants, operating at 33 MHz or 66 MHz. The possible bandwidth for a 32-bit PCI interface at 33 MHz is 133 MB/s, 266 MB/s for 66 MHz, and 532 MB/s for 64-bit PCI at 66 MHz. In contrast, the bandwidth of a PCIe card varies extensively, ranging from 250 MB/s to several GB/s per lane, depending on the card size and version. For more details, refer to the post “PCIe Card Tutorial: What Is a PCIe Card and How Do I Choose One?”
In other aspects, PCI Express supports up to 32 endpoint devices and supports hot plugging. Conversely, PCI does not allow hot plugging but can accommodate a maximum of five devices.
Frequently Asked Questions (FAQs) about PCI and PCI Express
1. Is PCI slower than PCI Express in terms of speed?
Yes, PCIe is faster than PCI. Consider PCIe x1, which provides at least a 118% speed increase compared to PCI. When comparing a PCIe-based video card to a PCI video card, the PCIe graphics chipset x16 type is nearly 29 times faster than the PCI video card.
2. Are PCI cards compatible with PCIe slots?
No, they are not. Due to their different configurations, PCIe and PCI are incompatible. Most motherboards have both PCI and PCIe slots, so it’s important to insert the card into the appropriate slot and avoid mixing the two types.
3. What is a PCIe slot?
A PCIe slot is the basic model of PCI Express. There are four types of slots: x16, x8, x4, and x1. The slot number increases with the length of the PCIe slot. For instance, PCIe x1 is 25 mm long, while PCIe x16 is 89 mm long.
Summary
In this article, we have compared PCI and PCI Express in terms of their origins, operating modes, bandwidth, and more. We have also provided answers to frequently asked questions about PCI and PCI Express. We hope this article has provided you with a better understanding of the distinction between PCI and PCI Express.
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