I
NTEL
® X
EON
® P
ROCESSOR
7500 S
ERIES
U
NCORE
P
ROGRAMMING
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UIDE
UNCORE PERFORMANCE MONITORING
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2.6 R-Box
Performance
Monitoring
2.6.1
Overview of the R-Box
The Crossbar Router (R-Box) is a 8 port switch/router implementing the Intel
®
QuickPath Interconnect
Link and Routing layers. The R-Box is responsible for routing and transmitting all intra- and inter-
processor communication.
The on-die agents include two B-Boxes (ports 4/7), two S-boxes (ports 2/6) and the U-Box (which
shares a connection with B-Box1 on Port7). The R-Box connects to these through full flit 80b links. Ports
0,1,4 and 5 are connected to external Intel QPI agents (through P-boxes also known as the physical
layers), also through full flit 80b links.
The R-Box consists of 8 identical ports and a wire crossbar that connects the ports together. Each port
contains three main sections as shown in the following figure: the input port, the output port, and the
arbitration control.
Figure 2-1. R-Box Block Diagram
2.6.1.1
R-Box Input Port
The R-Box input port is responsible for storing incoming packets from the B and S-Boxes as well as off-
chip requests using the Intel
®
QuickPath Interconnect protocol. Data from each packet header is
consolidated and sent to the R-Box arbiter.
R-Box input ports have two structures of important to performance monitoring; Entry overflow table
(EOT) and Entry Table (ET). R-Box PMU supports performance monitoring in these two structures.
2.6.1.2
R-Box Arbitration Control
The R-Box arbitration control is responsible for selecting when packets move from the input ports to the
output ports and which output port they go to if there are multiple options specified.
R-Box arbitration does not have any storage structures. This part of the logic basically determines
which port to route the packet and then arbitrate to secure a route to that port through the cross-bar.
The arbitration is done at 3 levels: queue, port and global arbitration. R-Box PMUs support performance
monitoring at the arbitration control.
Port 0 (QPI1)
Input
Output
Port 1 (QPI0)
Input
Output
Port 2 (S-Box0)
Input
Output
Port 3 (B-Box0)
Input
Output
Port 4 (QPI2)
Input
Output
Port 5 (QPI3)
Input
Output
Port 6 (S-Box1)
Input
Output
Port 7 (U/B-Box1)
Input
Output
L
Half
XBar
Half
XBar
R
Arb1
Arb0
Arb3
Arb2
Arb5
Arb4
Arb7
Arb6