Intel E7-4807 AT80615006432AB User Manual

Datasheet Volume 2 of 2

25

Each Intel Xeon Processor E7-8800/4800/2800 Product Families home agent integrates 
a global coherence engine that is the center of the coherency activity for the cache 
lines owned by that home agent. The Bboxes receive Home channel request and snoop 
responses from caching agents, and provides data response and completion to the 
system via Bbox to Router connection. Read and write commands to memory go out of 
the Bbox to the Memory Controller (MBox). 

 provides a Intel Xeon Processor E7-8800/4800/2800 Product Families block 

diagram including the Bbox.

The tracker table keeps track of coherency state at the home node for each transaction 
in-flight in the system (that has touched the home node). For each transaction that a 
caching agent injects into the system a tracker entry was statically preallocated at the 
home. The tracker allocation mode determines the particular preallocation during 
system initialization. The tracker allocation mode determines this statical partitioning of 
the tracker entries across the caching agents (Sboxes, IOHs, XNCs). There is a one-to-
one correspondence between a Transaction ID (TID) originating from a particular 
caching agent (Node ID=NID) and a tracker entry. In effect, each of the 256 tracker 
entries is statically mapped to a Transaction ID (TID), Node ID (NID) couple and vice-
versa.

(LLC Coherence Engine)

(Router)

30M Last Level Cache  (L3 Cache)

(Caching Agent 2)

(Home 

Agent 1)

(Home 

Agent 2)

(Memory 

Controller)

(Memory 

Controller)

(Physical 

Layer)

(Physical 

Layer)

(Caching Agent 1)

(Physical 

Layer)

(Physical 

Layer)

(Physical 

Layer)

(Physical 

Layer)

Dual Intel

®

SMI 

Channels

Dual Intel

®

SMI 

Channels

(Power Controller)

(System Config 

Controller)