Platform Power Requirements
R
94
Intel
®
855PM Chipset Platform Design Guide
Figure 46. Processor 1.8 V VCCA[3:0] Recommended Power Delivery and Decoupling
PRIMARY SIDE
VCCA0
VCCA3
VCCA1
VCCA2
GTLREF0
LAYER 3
1.8v from
855PM
PRIMARY SIDE
VCCA0
VCCA0
VCCA3
VCCA3
VCCA1
VCCA1
VCCA2
VCCA2
GTLREF0
GTLREF0
LAYER 3
1.8v from
855PM
1.8v from
855PM
1.8V from
Intel 855PM
MCH
PRIMARY SIDE
VCCA0
VCCA3
VCCA1
VCCA2
GTLREF0
LAYER 3
1.8v from
855PM
PRIMARY SIDE
VCCA0
VCCA0
VCCA3
VCCA3
VCCA1
VCCA1
VCCA2
VCCA2
GTLREF0
GTLREF0
LAYER 3
1.8v from
855PM
1.8v from
855PM
1.8V from
Intel 855PM
MCH
5.3.2.
Processor PLL Voltage Supply Power Sequencing
See Section 11.4.2 for more details on platform power sequencing requirements for the 1.8-V supply to
the processor and Intel 855PM MCH’s PLLs.
5.3.2.1.
Voltage Identification for Intel Pentium M/Intel Celeron M Processor
There are six voltage identification pins on the Intel Pentium M/Intel Celeron M processor. These
signals can be used to support automatic selection of V
CC-CORE
voltages. They are needed to cleanly
support voltage specification variations on current and future processors. VID[5:0] is defined in Table
19 below.
The VID[5:0] signals are 1.05-V CMOS level outputs. Intel recommends that 1:2 spacing and routing
with a trace impedance of 55
± 15% be used. No external termination is required for VID[5:0]. To
guarantee signal quality, a point-to-point routing between the Intel processor and the VRM should be
used. Figure 47 illustrates a signal escape routing example in the vicinity of the processor package
outline. To allow for the coexistence of V
CC-CORE
and V
CCP
power delivery routing as well as FSB signal
routing, the VID[5:0] signals should utilize the remainder of the routing channels on Layer 3 ( for VID2
and VID0), Layer 6 (for VID4), and Layer 8 (for VID1, VID3, and VID5).