PCI Express

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PCI Express

The common hardware interface in PCs, Macs and other computers for connecting peripheral devices such as storage drives and graphics cards. PCI Express (PCIe) was introduced in 2002 as "Third Generation I/O" (3GIO), and by the mid-2000s, motherboards had at least one PCIe slot for graphics. PCIe superseded PCI and PCI-X.

Switched Architecture - Multiple Lanes
Unlike its PCI predecessor, which used a shared bus, PCI Express is a switched architecture of up to 32 independent, serial lanes (x1-x32) that transfer in parallel. Each lane is full duplex (see illustration below).

Internal and External for Laptops
A mini PCIe came out for laptops (see Mini PCI Express) and Thunderbolt extends PCIe outside the computer (see external GPU). For PCIe/PCI comparisons, see PCI-SIG. See PC data buses, PCI, M.2, ExpressCard, Thunderbolt and PCI-X.
PCI Express   Data Rate (each direction)Version   1 Lane  4 Lanes  16 Lanes (MBps)        (GBps)

 Gen 1      250       1        4
 Gen 2      500       2        8
 Gen 3      984       3.94    15.85
 Gen 4     1969       7.88    31.51
 Gen 5     3938      15.75    63.02
 Gen 6**   7877      31.51   126.03 
  ** = planned for 2021

Parallel Transfer of Serial Channels
Each lane is an independent single-bit serial channel. PCIe is a type of parallel transfer but each lane has its own clock, which differentiates it from earlier parallel technologies.

PCIe on the Motherboard
This Asus motherboard has four x1 and three x16 slots (two black, one beige). The x16 slots accommodate x16, x8 and x4 cards. (Image courtesy of ASUStek Computer Inc.)

M.2 Over PCIe
This is a 960GB NVMe SSD on an 80x20mm M.2 card. The connection is via PCIe, either via an M.2 socket on the motherboard or a PCIe adapter card. See M.2.

Different Sizes of PCI Express
PCIe sockets are not the same as PCI, and they come in x1, x4, x8 and x16 sizes.

PCIe Replaced AGP for Graphics
The AGP slot gave way to an x16 PCIe slot for the graphics card. (Image courtesy of NVIDIA Corporation.)
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References in periodicals archive ?
The jitter methodology used in USB 3.0 is a Dual-Dirac model similar to that used in PCI Express. Limits are applied to the measurements per the USB 3.0 specification indicating a pass/fail result.
A wide range of NVIDIA's PCI Express architecture-based products were tested by PCI-SIG and judged to meet the PCI-SIG testing requirements, including:
Along with the PCI Express switch, Magma is also able to take advantage of IDT's extensive timing portfolio to complete the design of its ExpressBox7 x 8 Gen 2 expansion systems.
Euphonic needed an eight-lane PCI Express interface to meet the high bandwidth requirements of the EGC601 graphics controller, which supports up to five different imaging layers without intervention of the host CPU.
Other features include single-handed hard drive replacement and tool-free access to full height PCI and PCI Express x 16 expansion slots.
Serial Technologies Deliver New Capabilities for Next-Generation Server Storage Serial architectures, specifically Serial Attached SCSI (SAS), Serial ATA (SATA) and PCI Express, have emerged to deliver higher performance by allowing more bandwidth per device pathway than their parallel counterparts.
Up to four PCI Express X8 channels and four 1Gbps Ethernet links are supported through dual ServerWorks Hyper Transport 2000 chipsets, which together provide up to 4GB of bidirectional I/O.
PNY Technologies, Inc., has unveiled a full line of Verto GeForce graphics cards that capitalize on the PCI Express standard announced by the PCI Special Interest Group.
Broadcom Corporation (NASDAQ:BRCM), a provider of silicon solutions enabling broadband communications, has unveiled a new family of Broadcom NetXtreme Gigabit Ethernet (GbE) controllers that implement the advanced PCI Express host interface.