Intel i7-3920XM Extreme AW8063801009607 User Manual

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Datasheet, Volume 2

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Uncore

Port Arbitration Capability (PAC)
Indicates types of Port Arbitration supported by the VC resource. 

This field is valid for all Switch Ports, Root Ports that support 

peer-to-peer traffic, and RCRBs, but not for PCI Express Endpoint 

devices or Root Ports that do not support peer to peer traffic. 
Each bit location within this field corresponds to a Port Arbitration 

Capability defined below. When more than one bit in this field is 

set, it indicates that the VC resource can be configured to provide 

different arbitration services. 
Software selects among these capabilities by writing to the Port 

Arbitration Select field (see below).
Defined bit positions are:
Bit 0

Non-configurable hardware-fixed arbitration scheme, 

such as Round Robin (RR)

Bit 1

Weighted Round Robin (WRR) arbitration with 32 

phases

Bit 2

WRR arbitration with 64 phases

Bit 3

WRR arbitration with 128 phases

Bit 4

Time-based WRR with 128 phases

Bit 5

WRR arbitration with 256 phases

Bits 6-7

Reserved 

Processor only supported arbitration indicates "Non-configurable 

hardware-fixed arbitration scheme".