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24309E—March 2002
FLUSH# Pin
IGNNE# Pin
INIT# Pin
INTR Pin
JTAG Pins
K7CLKOUT and
K7CLKOUT# Pins
Key Pins
Chapter 10
Preliminary Information
The processor FID[3:0] outputs are open drain and 2.5 V
tolerant. To prevent damage to the processor, if these signals
are pulled High to above 2.5 V, they must be electrically
isolated from the processor. For information about the FID[3:0]
isolation circuit, see the AMD Athlon™ Processor-Based
Motherboard Design Guide, order# 24363.
See "Frequency Identification (FID[3:0])" on page 27 for the
DC characteristics for FID[3:0].
FLUSH# must be tied to VCC_CORE with a pullup resistor. If a
debug connector is implemented, FLUSH# is routed to the
debug connector.
IGNNE# is an input from the system that tells the processor to
ignore numeric errors.
INIT# is an input from the system that resets the integer
registers without affecting the floating-point registers or the
internal caches. Execution starts at 0_FFFF_FFF0h.
INTR is an input from the system that causes the processor to
start an interrupt acknowledge transaction that fetches the
8-bit interrupt vector and starts execution at that location.
TCK, TMS, TDI, TRST#, and TDO are the JTAG interface.
Connect these pins directly to the motherboard debug
connector. Pull TDI, TCK, TMS, and TRST# up to VCC_CORE
with pullup resistors.
K7CLKOUT and K7CLKOUT# are each run for two to three
inches and then terminated with a resistor pair: 100 ohms to
VCC_CORE and 100 ohms to VSS. The effective termination
resistance and voltage are 50 ohms and VCC_CORE/2.
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.
Pin Descriptions
AMD Athlon™ XP Processor Model 6 Data Sheet
71
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