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78 Pin Descriptions Chapter 11
AMD Athlon™ XP Processor Model 8 Data Sheet 25175H—March 2003
Preliminary Information
K7CLKOUT and
K7CLKOUT# Pins
K7CLKOUT and K7CLKOUT# are each run for two to three
inches and then terminated with a resistor pair: 100 ohms to
V
CC_CORE
and 100 ohms to VSS. The effective termination
resistance and voltage are 50 ohms and V
CC_CORE
/2.
Key Pins These 16 locations are for processor type keying for forwards
and backwards compatibility (G7, G9, G15, G17, G23, G25, N7,
Q7, Y7, AA7, AG7, AG9, AG15, AG17, AG27, and AG29).
Motherboard designers should treat key pins like NC (No
Connect) pins. A socket designer has the option of creating a
top mold piece that allows PGA key pins only where designated.
However, sockets that populate all 16 key pins must be allowed,
so the motherboard must always provide for pins at all key pin
locations.
See “NC Pins” for more information.
NC Pins The motherboard should provide a plated hole for an NC pin.
The pin hole should not be electrically connected to anything.
NMI Pin NMI is an input from the system that causes a non-maskable
interrupt.
PGA Orientation Pins No pin is present at pin locations A1 and AN1. Motherboard
designers should not allow for a PGA socket pin at these
locations.
For more information, see the AMD Athlon™ Processor-Based
Motherboard Design Guide, order# 24363.
PLL Bypass and Test
Pins
PLLTEST#, PLLBYPASS#, PLLMON1, PLLMON2,
PLLBYPASSCLK, and PLLBYPASSCLK# are the PLL bypass
and test interface. This interface is tied disabled on the
motherboard. All six pin signals are routed to the debug
connector. All four processor inputs (PLLTEST#, PLLBYPASS#,
PLLMON1, and PLLMON2) are tied to V
CC_CORE
with pullup
resistors.
PWROK Pin The PWROK input to the processor must not be asserted until
all voltage planes in the system are within specification and all
system clocks are running within specification.
For more information, Chapter 9, “Signal and Power-Up
Requirements” on page 45.