Intel Pentium D 945 HH80553PG0964MN User Manual

78

THERMTRIP#

Output

In the event of a catastrophic cooling failure, the processor will 
automatically shut down when the silicon has reached a 
temperature approximately 15°C above the maximum T

C

. Assertion 

of THERMTRIP# (Thermal Trip) indicates the processor junction 
temperature has reached a level beyond where permanent silicon 
damage may occur. Upon assertion of THERMTRIP#, the processor 
will shut off its internal clocks (thus, halting program execution) in 
an attempt to reduce the processor junction temperature. To protect 
the processor, its core voltage (V

CC

) must be removed following the 

assertion of THERMTRIP#. Driving of the THERMTRIP# signal is 
enabled within 10 µs of the assertion of PWRGOOD (provided 
VTTPWRGD, V

TT

, and V

CC

 are asserted) and is disabled on de-

assertion of PWRGOOD (if VTTPWRGD, V

TT

, or V

CC

 are not valid, 

THERMTRIP# may also be disabled). Once activated, THERMTRIP# 
remains latched until PWRGOOD, VTTPWRGD, V

TT

 or V

CC

 is de-

asserted. While the de-assertion of the PWRGOOD, VTTPWRGD, VTT 
or VCC signal will de-assert THERMTRIP#, if the processor’s junction 
temperature remains at or above the trip level, THERMTRIP# will 
again be asserted within 10 µs of the assertion of PWRGOOD 
(provided VTTPWRGD, V

TT

, and V

CC

 are asserted).

TMS

Input

TMS (Test Mode Select) is a JTAG specification support signal used 
by debug tools.

TRDY#

Input

TRDY# (Target Ready) is asserted by the target to indicate that it is 
ready to receive a write or implicit writeback data transfer. TRDY# 
must connect the appropriate pins/lands of all FSB agents.

TRST#

Input

TRST# (Test Reset) resets the Test Access Port (TAP) logic. TRST# 
must be driven low during power on Reset. 

VCC

Input

VCC are the power pins for the processor. The voltage supplied to 
these pins is determined by the VID[5:0] pins.

VCCA

Input

VCCA provides isolated power for the internal processor core PLLs.

VCCIOPLL

Input

VCCIOPLL

 

provides isolated power for internal processor FSB PLLs.

VCC_SENSE

Output

VCC_SENSE is an isolated low impedance connection to processor 
core power (V

CC

). It can be used to sense or measure voltage near 

the silicon with little noise.

VCC_MB_
REGULATION

Output

This land is provided as a voltage regulator feedback sense point for 
V

CC

. It is connected internally in the processor package to the sense 

point land U27 as described in the Voltage Regulator-Down (VRD) 
10.1 Design Guide for Desktop Socket 775.

VID[5:0]

Output

VID[5:0] (Voltage ID) signals are used to support automatic 
selection of power supply voltages (V

CC

). Refer to the Voltage 

Regulator-Down (VRD) 10.1 Design Guide for Desktop Socket 775 
for more information. The voltage supply for these signals must be 
valid before the VR can supply V

CC

 to the processor. Conversely, the 

VR output must be disabled until the voltage supply for the VID 
signals becomes valid. The VID signals are needed to support the 
processor voltage specification variations. See 

 for definitions 

of these signals. The VR must supply the voltage that is requested 
by the signals, or disable itself.

VSS

Input

VSS are the ground pins for the processor and should be connected 
to the system ground plane. 

VSSA

Input

VSSA is the isolated ground for internal PLLs.