Datasheet
Datasheet Volume 2 of 2 25
Home Agent and Global Coherence Engine (Bbox)
5 Home Agent and Global
Coherence Engine (Bbox)
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).
Figure 5-1 provides a Intel Xeon Processor E7-8800/4800/2800 Product Families block
diagram including the Bbox.
5.1 Tracker Allocation Modes
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.
Figure 5-1. Intel Xeon Processor E7-8800/4800/2800 Product Families Block Diagram
Core
3
Core
2
Core
4
Core
5
Core
6
Core
7
Core
8
Core
9
Cbox
(LLC Coherence Engine)
Rbox
(Router )
30M Last Level Cache (L3 Cache)
Sbox
(Caching Agent 2)
Bbox
(Home
Agent 1)
Bbox
(Home
Agent 2)
Mbox
(Memory
Controller)
Mbox
(Memory
Controller)
Pbox
(Physical
Layer)
Pbox
(Physical
Layer)
Sbox
(Caching Agent 1)
Pbox
(Physical
Layer)
Pbox
(Physical
Layer)
Pbox
(Physical
Layer)
Pbox
(Physical
Layer)
4 Intel® QPI links
Dual Intel
®
SMI
Channels
Dual Intel
®
SMI
Channels
Wbox
(Power Controller)
Ubox
(System Config
Controller)
Core
1
Core
10