Original 45nm Intel® Core™ Microarchitecture

Greater Mobility Through Lower Power

INTEL PROCESSORS BASED ON ORIGINAL 45NM INTEL CORE™ MICROARCHITECTURE

With the introduction of the Intel Penryn processors, Intel Corporation is providing a solution to realize thinner, cooler, and quieter systems. The Mobile Penryn family of processors provides an option for a full-performance component, but with a 10 W reduction in TDP from 35 W to 25 W. These parts were optimized to 25 W TDP in order to address the increasing focus on thermally constrained notebook designs.

Application to mobile systems

These new processors also bring a new level of opportunity for differentiation in the mainstream mobile market segment without sacrificing performance. The 10 W reduction in TDP that they provide as an option can be utilized at the system design level in one of four different ways:

• Thinner systems
• Cooler systems
• Quieter systems
• More feature-rich systems

Thinner systems

One of the primary directions in the mainstream mobile market is to build thinner systems. (Figure 4) illustrates this trend of notebook system thickness over time. As is shown with the dotted line in (Figure 4) , there is a somewhat linear relationship to this decrease in system thickness over time, and OEMs continue to look for opportunities to achieve thinner systems.

Figure 4: Notebook system thickness variation over time

However, as stated earlier, the thermodynamic limit for a particular system design is dependent on the air that flows through the system. In a horizontal fan configuration, also called blower fans, the volumetric air flow rate at a given speed is roughly proportional to the z-height of the fan and or blades.

This is an approximation, but it generally holds true for the horizontal fans in mobile systems. For a low-flow loss system, this applies roughly to the air flow rate associated with the operating point in the system. Therefore a reduction in available z-height results in a proportional reduction in air flow through the system.

In the example noted earlier, a 0.1” (2.5mm) reduction in total system thickness from 1.1” to 1” applies directly to the internal height available for the fan. Thus, a 2.5-mm reduction in the available fan height of a 12mm thick fan, results in a 20-percent reduction in air flow. For the nominal 3.3 cfm of the original system airflow, this translates to 0.6 cfm. From Equation 2 , this translates into approximately a 10 W effective system cooling capability.

Conversely then, if the required platform (base) power is reduced by 10 W, then the opportunity arises to make that system 0.1” (2.5mm) thinner.

The new lower-power Penryn family of mobile processors provides the OEM the ability to achieve this amount of reduction in z-height by providing an option for a TDP of 25 W, reduced from 35 W. This allows the mainstream market to more confidently target a new notebook thickness design point of 1” (14” display).

Cooler systems

An alternate use of the headroom provided by the new lower-power Penryn family of mobile processors is to make an existing industrial design cooler, whether by prescription or user choice. To evaluate the temperature reduction of a 10 W reduction in power provided by the Penryn family of mobile processors, we perform numerical simulations on the same nominal 14” display and 1.1”-thick system. The design features are summarized in Table 1, along with typical component TDP design powers, where TDP is representative of the highest power an individual component can go to under any realistic condition.

The simulation is performed using a Flotherm* model of the system. The grid varies in resolution in z and x-y, according to the proximity of component edges and air gaps. Most components are modeled as blocks with simple resistance planes between component and motherboard. Substantial validation has been performed on such models at Intel to establish a reasonable degree of confidence in the results for purposes of comparison.

When assessing how to design a cooler system, a stacked TDP methodology is not employed; rather, a system design power scenario is applied where the concurrent powers of each component are utilized. For purposes of comparison, consider a usage scenario in which the user is multitasking, stressing the processor and the platform as a whole with various concurrent activity (applications). The powers that we assume for such a scenario are summarized in Table 1. To evaluate the effect of the 10 W power reduction of the processor, the processor power is simply reduced from 35 W to 25 W, keeping all other TDPs at the same level, as denoted in Case 1 and 2, respectively.

Temperature results for the bottom surface are shown qualitatively in (Figure 5) , which illustrates a substantial reduction in warm area. Keep in mind that the scenario assumed is relatively stressful, and thus, warm. Some specific bottom surface (“skin”) temperatures are summarized in Table 2 .

click to enlarge

Figure 5: Simulation results–bottom surface (‘‘skin’’) temperature contours

From Table 2, a 10 W reduction in system power translates to approximately a 2°C reduction in skin temperature in the vicinity of the processor and its voltage regulator, and a 5.6°C reduction in exhaust air temperatures. Although these differences may not seem large, they can mean the difference between uncomfortable and unacceptable and make or break a design. Internal testing of various systems yielded similar results to the simulation.

Quieter systems

Another use of the additional thermal headroom provided by the 25 W version of the Penryn mobile processor is to allow for reduced maximum noise levels in a system.

Fans are usually turned on or their speed is increased when they are needed to support a high-power application or scenario (alternatively, to reduce the temperatures as discussed above). To evaluate the impact of the 10 W reduction in processor power, consider again the nominal system design in (Figure 1) , where you have a 14”-display and a 1.1” system thickness, with a corresponding maximum air flow rate of 3.3cfm in a user ambient temperature of 35°C and a maximum exhaust air temperature of 70°C.

Intel has internally tested many systems and the noise level associated with their flow rate under standard fan component test conditions.[3] Different flow rates are set by changing fan speed via the fan voltage. The resulting sensitivity of noise measured by sound pressure level is shown in (Figure 6) . A single fan result is shown by the dashed line in (Figure 6) . The boxed region indicates a range of system performance, roughly parallel to the single fan result shown. (Figure 6) further shows that a 1-cfm reduction in flow rate results in approximately a 10-dBA reduction in noise level.

Figure 6: Fan noise level sensitivity to flow-rate

Using Equation 3 for active cooling, we calculate that the air flow rate associated with the 10 W power reduction of the Penryn mobile processor is approximately 0.6cfm. Therefore, using the ∼10dBA cfm result from above, a 10 W reduction in power results in roughly a 6-dBA reduction in fan noise level. This is a noticeable reduction in noise to the user position, equivalent to moving the user position twice as far from the noise source.[4] Again, the actual noise level differences will depend upon the specific system design and the usage condition being considered.

More feature-rich systems

One interesting potential use of the TDP headroom provided by the new lower-power mobile Penryn family of processors is to allow other features in the platform to use this cooling capability. Some recipients of this power headroom could be better graphics performance, additional mini-card support (for more wireless cards), higher hotter system memory capabilities, etc. None of these expanded features could previously be attained within a predefined system design without one of the boundary conditions changing (that is, making the system larger or thicker).

The reduction in the use of power in this processor allows the remaining 10 W to be applied to these other features. For example, current notebook system designs devote approximately 5 W to cooling the system memory. This power limit of system memory prevents mobile platforms from being able to use the fastest (and therefore highest-temperature) memory technology. This is one of the reasons why mobile platforms do not support the same maximum system memory frequencies as desktop platforms. Applying the TDP delta to system memory would allow the OEM to add more features to the notebook system and help bridge some of the feature differences between desktop and mobile platforms.

Platforms based on those ingredients. Each of these opportunities further enhances the user experience of mobile computing and allows the mobile OEMs the ability to provide further innovations to enhance their own brand equity and thereby create a ‘win’ for both Intel and the OEM.

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