Intel G870 CM8062307260115 User Manual

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Datasheet, Volume 1

This section describes the PCI Express interface capabilities of the processor. See the 
PCI Express Base Specification for details of PCI Express.

The number of PCI Express controllers available is dependent on the platform:

• Processor with desktop Intel 5 Series Chipset: 1 x 16 PCI Express Graphics is 

supported.

• Processor with Intel 5 Series Chipset P55 and P57 SKUs: 2 x 8 PCI Express 

Graphics is supported.

• Processor with workstation Intel 3400 Series Chipset: 1 x 16 PCI Express Graphics 

or 2 x 8 PCI Express is supported (1 x8 primary port for graphics or I/O; 1 x 8 
secondary port for I/O only).

It defines the PCI Express port that is used as the external graphics attach. The port 
may also be referred to as PEG (or PEG0) and PCI Express Graphics Port.

Compatibility with the PCI addressing model is maintained to ensure that all existing 
applications and drivers operate unchanged.

The PCI Express configuration uses standard mechanisms as defined in the PCI Plug-
and-Play specification. The initial recovered clock speed of 1.25 GHz results in 
2.5 Gb/s/direction which provides a 250-MB/s communications channel in each 
direction (500 MB/s total). That is close to twice the data rate of classic PCI. The fact 
that 8b/10b encoding is used accounts for the 250 MB/s where quick calculations would 
imply 300 MB/s. The PCI Express ports support 5.0 GT/s speed as well. Operating at 
5.0 GT/s results in twice as much bandwidth per lane as compared to 2.5 GT/s 
operation. 

The PCI Express architecture is specified in three layers: Transaction Layer, Data Link 
Layer, and Physical Layer. The partitioning in the component is not necessarily along 
these same boundaries. Refer to 

 for the PCI Express Layering Diagram.