Intel Xeon Processor and Intel E7500/E7501Chipset Compatible Platform Design Guide
System Bus Routing Guidelines
82 Intel
®
Xeon™ Processor and Intel
®
E7500/E7501 Chipset Compatible Platform Design Guide
The BSEL0 output from the processor 0 socket is also connected to the CK408B and GPI to
program both devices to operate at either 100 MHz or 133 MHz based on the processor installed.
Table 5-13 summarizes the operation of the reference circuit.
NOTE: VID[4:0] have been omitted from this table to simplify the description. Described functionality assumes
that VID values match when both processors are installed. In the event where VID values do not match,
the circuit will disable the voltage regulator to prevent unsupported processor operation.
Figure 5-13. BSEL[1:0] Reference Circuit
Table 5-13. Functionality of SKTOCC# and VR Output
Processor 0
Socket
Processor 1
Socket
SKTOCC#
VR Output
Low = Disable
High = Enable
Functionality
533 MHz System
Bus Processor
533 MHz System
Bus Processor
LH
Operates system in DP mode with
133 MHz system bus clock.
400 MHz System
Bus Processor
533 MHz System
Bus Processor
LL
Disables voltage regulator to
prevent processor operation.
533 MHz System
Bus Processor
400 MHz System
Bus Processor
LL
Disables voltage regulator to
prevent processor operation.
400 MHz System
Bus Processor
400 MHz System
Bus Processor
LH
Operates system in DP mode with
100 MHz system bus clock.
533 MHz System
Bus Processor
None H H
Operates system in UP mode with
133 MHz system bus clock.
None
533 MHz System
Bus Processor
LL
Disables voltage regulator to
prevent processor operation.
400 MHz System
Bus Processor
None H H
Operates system in UP mode with
100 MHz system bus clock.
None
400 MHz System
Bus Processor
LL
Disables voltage regulator to
prevent processor operation.
VID_P0[4:0]
CPU0_BSEL[1:0]
VID_P1[4:0]
CPU1_BSEL[1:0]
BSEL0
Any GPI
1 kΩ
+3.3V
1 kΩ
+3.3V
1 kΩ
+3.3V
1 kΩ
+3.3V
Comparator
74HC682
P=Q
+3.3 V
74HC03D
CPU1 -
SKTOCC-N
VR Control
Low = Disable
High = Enable
Processor 0
SKTOCC 0
VID[4:0]
BSEL[0:1]
Processor 1
SKTOCC 1
VID[4:0]
BSEL[0:1]
1 kΩ
CK408B
S1
55
10 kΩ