Figure 20. Cpu Maximum Current Draw For Heat Exchanger Fan Speed; Table 9. Maximum Estimated Processor Current Capability At 35 ºc External - Intel QX9770 - Core 2 Extreme Quad-Core Processor Design Manual

Using the cooling approach on the Intel D975XBX2 Desktop Board the CPU current
draw vs. heat exchanger fan speed is shown in Figure 20 and Table 9 as well as the
performance of not having this cooling feature. This was measured as the maximum
current draw before the VR circuitry reaches its maximum temperature and asserts
the PROCHOT# signal.
The socket has a maximum temperature specification to maintain proper electrical
performance at the contacts. Based on this temperature the current capability is
slightly reduced but still shows improved capability of over 20 A at 100% speed over
not having this feature.

Figure 20. CPU Maximum Current Draw for Heat Exchanger Fan Speed

Table 9. Maximum Estimated Processor Current Capability at 35 ºC External Ambient
25% – VR Requirements
60% – VR Requirements
100% – VR Requirements
100% – Socket Requirements
NOTES:
1.
56
CPU maximum current draw capability
VR/Socket Cooling Feature
190
180
170
160
150
140
130
120
110
100
0% 20%
Heat Exchanger Fan Speed (PWM)
Fan Speed (PWM)
(1)
Socket temperature requirement is based on the maximum temperature necessary for
end of life socket electrical performance
LGA775 Socket Heatsink Loading
at 35C external ambient
No Cooling Feature
40% 60% 80%
Max. Current Draw for
Heat Exchanger with VR
and Socket Airflow
Cooling Feature (A)
115
150
180
165
§
Thermal and Mechanical Design Guidelines
100% 120%
Max. Current Draw
for Heat Exchanger
and fan with no
Cooling Feature (A)
105
120
150
140