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80 Pin Descriptions Chapter 11
AMD Athlon™ XP Processor Model 8 Data Sheet 25175H—March 2003
Preliminary Information
For more information, see the “Required Circuits” chapter of
the AMD Athlon™ Processor-Based Motherboard Design Guide,
order# 24363.
VREFSYS Pin VREFSYS (W5) drives the threshold voltage for the system bus
input receivers. The value of VREFSYS is system specific. In
addition, to minimize V
CC_CORE
noise rejection from VREFSYS,
include decoupling capacitors. For more information, see the
AMD Athlon™ Processor-Based Motherboard Design Guide, order#
24363.
ZN and ZP Pins ZN (AC5) and ZP (AE5) are the push-pull compensation circuit
pins. In Push-Pull mode (selected by the SIP parameter
SysPushPull asserted), ZN is tied to V
CC_CORE
with a resistor
that has a resistance matching the impedance Z
0
of the
transmission line. ZP is tied to VSS with a resistor that has a
resistance matching the impedance Z
0
of the transmission line.
Table 28. VID[4:0] Code to Voltage Definition
VID[4:0]
V
CC_CORE
(V)
VID[4:0]
V
CC_CORE
(V)
00000 1.850 10000 1.450
00001 1.825 10001 1.425
00010 1.800 10010 1.400
00011 1.775 10011 1.375
00100 1.750 10100 1.350
00101 1.725 10101 1.325
00111 1.675 10111 1.275
01000 1.650 11000 1.250
01001 1.625 11001 1.225
01010 1.600 11010 1.200
01011 1.575 11011 1.175
01100 1.550 11100 1.150
01101 1.525 11101 1.125
01110 1.500 11110 1.100
01111 1.475 11111 No CPU