Intel Pentium 4 Processor In the 423-pin Package Thermal Design Guidelines
Pentium® 4 Processor in the 423-pin Package Thermal Design Guidelines
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8.4 System Considerations
The Thermal Monitor feature may be used in a variety of ways, depending upon the system design requirements and
capabilities. Intel requires the thermal control circuit to be enabled for all Pentium® 4 processor systems. At a
minimum, the thermal control circuit supplies an added level of safety against loss in processor availability due to an
over temperature situation.
Each application program, which is comprised of thousands of processor instructions, will have its own unique
power profile, although the profile will have some variability due to loop decisions, I/O activity and interrupts. In
general, compute intensive applications with a high cache hit rate will dissipate more processor power than
applications that are I/O intensive or have low cache hit rates.
In order to gain a more thorough understanding of application power levels, Intel has estimated the power
dissipation of a number of popular software applications. The method involved required extraction of actual code
sequences from the programs and calculating the power consumed if that program were to be run on a Pentium 4
processor. Code sequences, or traces, were gathered from roughly 200 applications and benchmarks. These included
Transaction Processing Performance Council TPC-C, SPEC*, SPECint* SPECfp, SPECweb, Ziff-Davis*
3Dwinbench* and Winstone*, Microsoft* desktop applications, id Software* Quake*, CorelDraw*, Video playback
with Intel® MMX™ enhanced technology, several of which were run under multiple operating systems. (Including
Microsoft Windows* 98, Microsoft Windows NT* and Linux*) and other compute intensive applications. See
Figure 12 for a sample distribution of application power.
Processor power dissipation simulations indicate a maximum application power in the range of 75% of the
maximum power for a given frequency. Therefore, a system designed to the thermal design point, which has been
set to approximately 75% of the maximum processor power would be unlikely to see the thermal control circuit
active and experience the associated performance reduction. Systems designed for lower power dissipation could be
subject to activation of the thermal control circuit depending upon ambient air temperature and software application
power profile. Figure 13 plots processor performance with the Thermal Control Circuit enabled versus system
cooling capability. System designers must evaluate the tradeoffs between cooling costs and risk of processor
performance loss to determine the optimum configuration for the end user.
Figure 12. Application Power Dissipation Estimates for the Pentium 4 processor
0
10
20
30
40
50
0%
8%
16%
24%
32%
40%
48%
56%
64%
72%
80%
88%
96%
# Trace
s
Pentium 4
processor thermal
design point
Maximum
Power