Compaq Deskpro 4000 - 7.3.2 LOW VOLTAGE DISTRIBUTION

Technical Reference Guide
Compaq Deskpro 4000 and 6000 Personal Computers
featuring the Pentium II Processor
First Edition - October 1997
7-5
7.3.2 LOW VOLTAGE DISTRIBUTION
Voltages less than 3.5 VDC are produced through regulator circuitry on the system board.
Figure 7–3.
Low Voltage Supply, Block Diagram
The VccP regulator produces the VccP (Pentium Pro processor core) voltage according to the
state of the VID4..0 signals from the Pentium II microprocessor. This allows automatic selection
of the proper core voltage depending on the installed microprocessor component. The possible
voltages available are listed as follows:
VID4..0 VccP VID4..0 VccP VID4..0 VccP
10000 3.5 VDC 11000 2.7 VDC 00000 2.05 VDC
10001 3.4 VDC 11001 2.6 VDC 00001 2.00 VDC
10010 3.3 VDC 11010 2.5 VDC 00010 1.95 VDC
10011 3.2 VDC 11011 2.4 VDC 00011 1.90 VDC
10100 3.1 VDC 11100 2.3 VDC 00100 1.85 VDC
10101 3.0 VDC 11101 2.2 VDC 00101 1.80 VDC
10110 2.9 VDC 11110 2.1 VDC 00110-01111 Reserved
10111 2.8 VDC 11111 CPU not installed
VccP
1.5 VDC
Regulator
Circuit
+12 VDC
2SK1388
VID0
To
Pentium II
Processor
VID1
VID2
VID3
From
Pentium II
Microprocessor
+3.3 VDC
VTT
(
+1.5 VDC
)
Regulator
Circuit
+12 VDC
Power Supply
Microprocessor
2SK2248S
+5 VDC
VID4
+5 VDC