Intel Pentium 4 Processor on 90 nm Process Thermal and Mechanical Design Guidelines

Thermal Requirements
R
32 Intel
®
Pentium
®
4 on 90 nm Process Thermal Design Guide
3.5.3 How On-die Thermal Diode, T
CONTROL
and Thermal Profile
work together
The Pentium 4 processor on 90 nm process thermal specification is comprised of the two
parameters, T
CONTROL
and thermal profile. The first step is to ensure the thermal solution by design
meets the thermal profile. If the system design will incorporate variable speed fan control Intel
recommends monitoring the on-die thermal diode to implement acoustic fan speed control. The
value of the on-die thermal diode temperature determines which specification must be met.
3.5.3.1 On-die Thermal Diode less than T
CONTROL
When the thermal solution can maintain the thermal diode temperature to less than T
CONTROL
, then
T
C
is not specified.
3.5.3.2 On-die Thermal Diode greater than T
CONTROL
When the on-die thermal diode temperature exceeds T
CONTROL
, then the thermal solution must meet
the thermal profile for T
C
.for that power dissipation.
3.6 Acoustic Fan Speed Control
Higher processor power can increase the thermal requirement and can, therefore, generate
increasingly more noise. Intel has added an option to the processor thermal specifications that
allows the system integrator to have a quieter system in the most common usage condition.
T
CONTROL
and the on-die thermal diode provide the system integrator the means to implement a
quieter system design.
Acoustic fan control implementations consist of the following items:
• A motherboard design with a fan speed controller with Pulse Width Modulation (PWM)
output and remote thermal diode measurement capability. Consequently, the motherboard has
a 4 pin fan header for the processor heatsink fan.
• A processor heatsink with a 4 wire PWM controlled fan.
Fan speed control and PWM output are embedded in a number of components from major
manufacturers. These components can be stand alone or a Super IO (SIO). The following vendors
have components that would be suitable: Analog Devices*, ITE*, National Semiconductor,
SMSC*, and Winbond*. Consult their web sites or local sales representatives for a part suitable
for your market needs.