
Chapter 10
Pin Descriptions
65
23792I—June 2001
AMD Athlon Processor Model 4 Data Sheet
Preliminary Information
FLUSH# Pin
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# Pin
IGNNE# is an input from the system that tells the processor to
ignore numeric errors.
INIT# Pin
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 0FFFF FFF0h.
INTR Pin
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.
JTAG Pins
TCK (Q1), TMS (Q3), TDI (U1), TRST# (U3), and TDO (U5) are
the JTAG interface. Connect these pins directly to the
motherboard debug connector. Pullup TDI, TCK, TMS, and
TRST# to VCC_CORE with pullup resistors.
K7CLKOUT and
K7CLKOUT# Pins
K7CLKOUT (AL21) and K7CLKOUT# (AN21) are each run for 2
to 3 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.
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
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.
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.