Intel Core2 Duo Desktop Processor, Intel Pentium Processor, and Intel Pentium 4 Processor 6x1 Sequence

Intel® Enabled Balanced Technology Extended (BTX) Reference solution

Thermal and Mechanical Design Guidelines 45

5.1.5 Altitude

The reference TMA was evaluated at sea level. However, many companies design

products that must function reliably at high altitude, typically 1,500 m [5,000 ft] or

more. Air-cooled temperature calculations and measurements at sea level must be

adjusted to take into account altitude effects like variation in air density and overall

heat capacity. This often leads to some degradation in thermal solution performance

compared to what is obtained at sea level, with lower fan performance and higher

surface temperatures. The system designer needs to account for altitude effects in the

overall system thermal design to make sure that the T

requirement for the processor

is met at the targeted altitude.

5.1.6 Reference Heatsink Thermal Validation

The Intel reference heatsink was validated within the specific boundary conditions

based on the methodology described in Section

5.2 , and using a thermal test vehicle.

Testing is done in a BTX chassis at ambient lab temperature. The test results, for a

number of samples, is reported in terms of a worst-case mean + 3σ value for thermal

characterization parameter using real processors (based on the thermal test vehicle

correction factors).

5.1.7 Fan Performance for Active Heatsink Thermal Solution

The fan power requirements for proper operation are given Table 6.

Table 6. Fan Electrical Performance Requirements

Requirement Value

Maximum Average fan current draw 1.5 A

Fan start-up current draw 2.2 A

Fan start-up current draw maximum duration 1.0 second

Fan header voltage 12 V ±5%

Tachometer output 2 pulse per revolution

In addition to comply with overall thermal requirements (Section 6.1.1), and the

general environmental reliability requirements (Section 6.2) the fan should meet the

following performance requirements:

• Mechanical wear out represents the highest risk reliability parameter for fans. The

capability of the functional mechanical elements (ball bearing, shaft, and tower

assembly) must be demonstrated to a minimum useful lifetime of 40,000 hours.

• In addition to passing the environmental reliability tests described in Section

6.2,

the fan must demonstrate adequate performance after 7,500 on/off cycles with

each cycle specified as 3 minutes on, 2 minutes off, at a temperature of 70 °C.

See the Fan Specification for 4-wire PWM Controlled Fans for additional details on the

fan specification.