Are you confused about PCI and PCIe? If you don’t know how to distinguish them, you can read this article which explains their differences in 4 aspects: functionality, appearance, speed, and compatibility.
What are PCI and PCI Express?
In a computer, if different devices want to exchange data, they must do so over a certain channel (i.e., a bus). A bus is a universal communications backbone used to transfer information between the various functional components of a computer. It is a transmission harness composed of wires. PCI and PCIe are both buses.
What does PCI do in a PC?
PCI is the abbreviation of Peripheral Component Interconnect, which is the local bus in PC. So, how does it work on a computer?
In this motherboard, the Northbridge is fully integrated into the CPU, so there are only two main parts: the CPU and the Southbridge (hub or platform controller hub). Likewise, the graphics card and memory are connected directly to the CPU. But there are two points you should pay attention to the graphics card is connected to the CPU through the PCIe bus; b. The motherboard supports a direct connection between the CPU and PCIe SSD. The chipset (Southbridge) is then connected to the CPU via the DMI (Direct Media Interface) 3.0 bus based on the PCIe bus. The Southbridge distributes 24 PCIe lanes for connecting hard drives, USB devices, network cards, sound cards, and more. It can be said that PCIe is more than just a local bus. It is already the system bus.
PCI and PCIe slots
In this part, I’ll show you what PCI and PCIe slots look like. PCI Slot: This slot comes in two types: a 124-bit slot with 32 pins and an 188-bit slot with 64 pins. The former is usually used for general desktop computers, and the latter is usually used for servers.
PCIe: This slot comes in 7 versions: x1, x2, x4, x8, x12, x16 and x32, corresponding to 1/2/4/8/12/16/32 lanes respectively. Among them, PCI-E x32 has almost no corresponding mass-produced products due to its large size and is only used on special occasions. PCI-E x12 is mainly used in servers and will not appear on consumer platforms. PCI-E x2 is primarily for internal interfaces, not expansion slots. Even though some motherboards offer this connector, PCI-E x2 comes in the form of an M.2 connector rather than a PCI-E slot.
Therefore, the mainstream PCI-E slots on motherboards are concentrated in four types: PCI-E x1/x4/x8/x16. They are described in more detail below:
PCI-E x16 slot: It is 89 mm long and has 164 pins. It is typically used with graphics cards and is backward compatible with x1/x4/x8 devices.
PCI-E x8 slot: It is 56 mm long and has 98 pins. It usually comes in the form of a PCI-E x16 slot, but only half of the data pins are active, meaning the actual bandwidth is only half that of a real PCI-E x16 slot. The purpose is to allow the graphics card with the PCI-E x16 interface to be successfully installed on the PCI-E x8 interface.
PCI-E x4 slot: It is 39 mm long and has 64 pins. It is mainly used to install PCI-E SSD or M.2 SSD (via PCI-E adapter). But in most cases, PCI-E x4 slots come from the factory as M.2 connectors.
PCI-E x1 slot: It is only 25 mm long and has 36 pins. The target products are relatively broad, including independent network cards, independent sound cards, USB 3.0/3.1 expansion cards, etc.
PCI vs PCIe speed
32-bit PCI speed is 133 MB/s, while 64-bit PCI speed is 266 MB/s.
Currently, most computers use PCIe version 3.0. With this version, even PCIe x1 can be much faster than 64-bit PCI. In terms of PCI vs PCI-E speed, PCI-E is the winner and it completely replaces PCI.
PCI and PCIe compatibility
PCI: 32-bit PCI interfaces are not compatible with 64-bit PCI products, while 64-bit PCI interfaces are compatible with 32-bit PCI products.
PCIe: PCI-E interfaces come in different lengths. The more lanes it has, the longer the interface. Generally, long slots are compatible with short-interface products. For example, a PCIe X16 slot can be compatible with X4 or X8 products. However short slots are not compatible with long interface products because they cannot be inserted.
PCIe: PCIe comes in different versions. Different versions are compatible with each other. For example, PCIe 3.0 is compatible with PCIe 2.0. But the performance is determined by the lower version.
PCI vs PCIe: PCI-E interface and PCI interface are not compatible with each other.
PCIe Gen4 with ReDriver to Oculink SFF-8612 Adapter Card
PCIe 3.0 x4 to Oculink SFF-8612 Adapter Card
PCIe 3.0 x4 to U.2 Expansion Card with Mini SAS SFF-8643 36Pin Female Ports
PCIe 3.0 x8 to U.2 Expansion Card with Dual Mini SAS SFF-8643 36Pin Female Ports
PCIe 3.0 x4 to SFF-8654 Slimline SAS Expansion Card
PCIe 3.0 x4 to 24 Ports SATA 6G Card with 3 Slim SAS SFF-8654 8i 74P
M.2 NVME to 2 SFF 8087 Expansion Card
M.2 NVME to SFF 8087 Expansion Card
LSI 9217-4i4e IT Mode RAID Controller Card
PCIe x4 to 4 Ports SAS SATA RAID Controller Card
About Shenzhen STC Electronic Co., Ltd
STC-CABLE is an industry-leading manufacturer of high-performance cabling and connectivity solutions. Founded in 2008, STC provides end-to-end connectivity solutions serving a variety of markets–including corporate, digital signage, education, healthcare, home theater, and hospitality.
As a professional cable assembly factory, STC brings a complete portfolio of products and solutions including USB 2.0 Cables, USB 3.0 Cables, USB C Cables, Drive Cables, Network Cables & Adapters, Audio & Video Cables, Serial & Parallel Cables, Audio-Video Products, Computer power Cables internal and so on.
Leo Zhang
Sales Manager
leo@stccable.com
Tel: (86) 0755 2321 4701
(86) 134 2285 3610
www.stc-cable.com
STC Electronic (Hong Kong) Co., Limited
Shenzhen STC Electronic Co., LTD
