System Bus Routing Guidelines
64
Design Guide
The SM_TS_A[1:0] signals set the SMBus address for the thermal device on the processor. These
signals must be set at power up with a unique address per bus. The SM_TS_A[1:0] can be set to
logic high, logic low, or a high impedance state giving nine possible combinations of addresses.
Refer to the section on SMBus Device Addressing in the Processor datasheet for addressing details.
The SM_TS_A[1:0] signals do not have an internal pull-down and thus must be pulled to VSS or
SM_VCC with a 1 k
Ω
± 5% or smaller resistor. Leaving the pins floating achieves a high-Z state.
The SM_WP signal is a write protect signal for the memory device. Pulling this signal to SM_VCC
with a 100
Ω
± 5% resistor enables write protection. SM_WP has an internal 10 k
Ω
pull-down.
5.3.5
System Bus COMP Routing Guidelines
Terminate the processor COMP[1:0] pins to ground through 50
Ω
± 1% resistors. Do not wire the
COMP pins together—connect each pin to its own termination resistor.
Terminate the MCH HXRCOMP and HYRCOMP with a 25
Ω
± 1% resistor pull-down to ground.
Terminate the MCH HXSWING and HYSWING using a 150
Ω
± 1% resistor pull-down to ground,
and a 301
Ω
± 1% pull-up to VCC_CPU, respectively. Use two 0.01
µ
F decoupling capacitors.
5.3.6
BR[3:0]# Routing Guidelines
Connect BR[3:0]# as shown in
. The total bus length must be less than 20.2". BR3# and
BR2# are not used and are pulled to VCC_CPU.
5.3.7
ODTEN Signal Routing Guidelines
Processor 0, the end processor in a dual processor system, must have its on-die termination
enabled. The termination value must be within 20% of the signal impedance (50
Ω
± 20%). To
enable the on-die termination, pull the ODTEN pin to a high state by terminating it to VCC_CPU
through a 50
Ω
± 20% resistor. Processor 1, the middle agent, must have its on-die termination
disabled. To disable on-die termination, pull the ODTEN pin to a low state by terminating it to
ground through a 50
Ω
± 20% resistor.
Figure 5-10. BR[3:0]# Connection for DP Configuration
Table 5-7. BR[3:0]# Connection
Trace
Impedance
L1
Processor-
to-Processor
L2
Processor1
BR1# to
Intel
®
MCH
L3
Processor-
to-R
T
Stub
L4
Processor-to-
R
PU
Stub
R
T
R
PU
50 Ω
3.0 – 10.0”
15.7” max
1” max
3” max
50
Ω
± 5%
50
Ω
± 5%
MCH
Processor 1
BR0
#
BR1
#
BR2
#
BR3
#
BR0
#
BR1
#
BR2
#
BR
3
#
VCC_CPU
Rpu
Processor 0
L1
L2
L4
VCC_CPU
BREQ0#
R
T
R
T
R
T
L3
L3
L3
Summary of Contents for Xeon
Page 24: ...Introduction 24 Design Guide This page is intentionally left blank ...
Page 30: ...Component Quadrant Layout 30 Design Guide This page is intentionally left blank ...
Page 52: ...Platform Clock Routing Guidelines 52 Design Guide This page is intentionally left blank ...
Page 66: ...System Bus Routing Guidelines 66 Design Guide This page is intentionally left blank ...
Page 118: ...Intel 82870P2 P64H2 118 Design Guide This page is intentionally left blank ...
Page 146: ...I O Controller Hub 146 Design Guide This page is intentionally left blank ...
Page 148: ...Debug Port 148 Design Guide This page is intentionally left blank ...
Page 210: ...Schematic Checklist 210 Design Guide This page is intentionally left blank ...
Page 220: ...Layout Checklist 220 Design Guide This page is intentionally left blank ...
Page 222: ...Schematics 222 Design Guide This page is intentionally left blank ...