What is PCI Express?

One of the most significant changes to come to PC systems in a decade, PCI Express is a new interconnect technology designed to provide universal connectivity for use as a chip-to-chip and chip to adapter card interconnect. PCI Express architecture provides for extremely high bandwidth at low cost.

PCI Express can offer up to 70 times the bandwidth of today's PCI architecture and is scaleable for the future. PCI Express will be featured across all Intel platforms including desktop, server, workstation and in the latter half of 2004 with mobile platforms as well.  PCI Express will be the I/O architecture for everything from graphics adapters to Ethernet cards to TV tuners. This massive bandwidth will alleviate many current and future performance bottlenecks on the adapter bus.

PCI Express is based on a type of serial communications technology somewhat like that in USB or SATA hard drives.  The mechanical (physical) board connectors come in one of four types: x1, x2, x4, and x16 (see illustration to the right) in order to meet different peak bandwidth requirements.

PCI Express Technical Specs:

• Full duplex point-to-point topology
• Differential low voltage interconnect
• Embedded clocking
• Scalable frequency: Initial Bit Rate: 2.5Gb sec/lane/direction
• Scalable bandwidth - data layer is scalable to 1x, 2x, 4x, 8x, 12x, 16x, 32x lane widths
• Each PCI Express "lane" uses 4 wires - one differential pair for transmit and one pair for receive

* Note: PCI Express is NOT the same as PCI-X slots, it is a totally new technology.

Key Advantages of PCI Express

PCI express is a highly flexible, reliable, modular and scalable design that will eventually replace all PCI slots on the motherboard and AGP slots.  It has better power management, native hot-plug support, backwards compatibility with PCI software, support for streaming media (such as video camera or TV), and truly scalable configurations. In addition:

• Compatible with existing PCI drivers and software and operating systems
• High bandwidth per pin. Low overhead. Low latency
• Ability to scale speeds by forming multiple lanes
• A point-to-point connection, allows each device to have a dedicated connection without sharing bandwidth
• Ability to comprehend different data structures
• Low power consumption and power management features
• Hot swap-ability and hot plug-ability for devices
• Supported by nearly 500 system hardware vendor

The x1 PCI Express slots will easily replace the standard 32-bit PCI slots and have four times the bandwidth.

The high-performance x16 configuration will have up to 4GB/sec bandwidth (8GB/sec concurrent) to replace AGP technology and will also have four times the bandwidth of AGP 8x!

With the advent of PCI Express video cards whole new worlds of 3D gaming and superior graphics performance will be possible.  ATI has already developed RADEON video cards using PCI express architecture and in just a short couple years will be the dominant video card interface and only choice for 3D graphics power users. ATI’s video processors have a native, or “true” PCI Express interface. They can communicate directly with the PCI Express bus at PCI Express speeds (do not need to use a bridge).