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Introduction to PCI Express: the AGP8X Replacement
Introduction to PCI Express: the AGP8X Replacement - PCSTATS
Like AMD's Hypertransport technology, PCI Express is a 2-way, serial connection that carries data in packets, similar to the way it is transferred over Ethernet connections.
Filed under: Video Cards Published:  Author: 
External Mfg. Website: PCI Express Org Dec 11 2003   M. Dowler  
Home > Reviews > Video Cards > PCI Express Org

Videocard Capabilities

Currently, PCI Express X16 provides up to 75W of power for video cards, as opposed to the current 25W/42W allowed by AGP8X. Most modern cards already consume more than this amount, as evidenced by the extra power connectors that appear on today's AGP high-end video cards. This explains why most modern midrange PCI-Express videocards do not require extra power connectors, while their AGP counterparts do.

Given that both ATI and Nvidia have virtually switched over to PCI Express and that major graphics companies from 3Dlabs to XGI have already announced support for the architecture, it looks like AGP's days are inevitably drawing to a close. To further depreciate the value of your very expensive AGP cards, PCI Express X16 and 8x AGP slots cannot coexist properly on the same motherboard. This fact has not stopped various motherboard manufacturers from releasing ersatz PCIe/AGP solutions that use the PCI bus or part of the PCI Express bus. While this provides a better incentive to upgrade for AGP card users, it should be noted that these solutions do not provide the full bandwidth of a real AGP8x slot.

What makes up the PCI Express bus?

The PCI Express bus is composed of multiple lanes of point-to-point wired copper interconnects serving all the components that used to just drop data into the older PCI bus. To make things even more flexible, a switch has been added to the architecture.

Working in principle just like an Ethernet switch, this sits between the PCI Express devices connected to the board and the rest of the I/O system. This will enable newer devices, for example PCI Express connected on board Gigabit controllers or 10/100 gigabit network cards, to communicate with each other directly if necessary. By adding in this shortcut the data need not go through the chipset to reach an adjacent device.

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Contents of Article: PCI Express Org
 Pg 1.  Introduction to PCI Express: the AGP8X Replacement
 Pg 2.  What does PCI Express mean to your PC?
 Pg 3.  — Videocard Capabilities
 Pg 4.  Compatibility between PCI 2.2 and PCI Express
 Pg 5.  PCI Express X1, X2, X4, X8, X16
 Pg 6.  External PCI Express devices road mapped

 
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