Original 45nm Intel® Core™ Microarchitecture

Power Improvements on 2008 Desktop Platforms

RESULTS

All the power-saving techniques described in the previous sections implemented on the 2008 desktop platform contribute to a more energy-efficient platform. (Figure 1) shows that a system spends most of its time at or near idle, and power saved under these conditions is critical to achieve energy efficiency. In this section we present DC component and AC platform power data to demonstrate the power-management improvements of the 2008 platform. We also explore the impact of USB devices, such as the keyboard and mouse, on platform power management. Finally, we present some best known methods for getting the most out of the new platform power-management features.

The 2008 platform achieves significant idle and low utilization power savings from its support of deeper C-states (up to C4 state versus the 2007 desktop platform which supports only C2). The support for deeper C-states allows enabling of additional power-management techniques for major components in the desktop platform, ultimately leading to a 16-percent reduction in platform power (varies from platform to platform depending on the components in the platform) in idle and a 5-percent reduction when running Sysmark 2007.

(Figure 6) illustrates the AC power savings achieved as well as the DC savings at the component level under idle conditions. Note that there is nearly a 60-percent power savings for the Yorkfield processor, mostly attributed to a dramatic reduction in core voltage when in C4. Beyond the processor itself, since C4 is a synchronized effort between major silicon components in the platform, the Intel Q45 Express Chipset achieves a 28-percent power improvement. This DC savings will vary from processor to processor and chipset to chipset due to natural distributions of static current and the way C4 voltage settings are optimized by manufacturing on a part-by-part basis. The system memory achieves a 60-percent power improvement, because the chipset puts the memory in a self-refresh state as previously explained. These component-level power savings, along with the efficiency improvements on VRD11.1 power delivery (described earlier), add up to an approximate 16-percent power improvement at the platform level.

Figure 6: Platform and component power savings

The shift in C-states residency between 2007 and 2008 platforms is illustrated in (Figure 7) . Generally, C-state residency numbers give an indication of how much time as a percentage the platform spends in each C state. The 2007 platform has the ability to utilize only C2, and (Figure 7) shows that the platform spends 99 percent of its time in C2 under idle conditions. Much of that time spent in C2 converts directly to C4 time on the 2008 platform, but not all of it. On the 2008 platform, (Figure 7) shows a remainder of 11 percent in C2 and C4 state residency of 88 percent. This change in the distribution of deep C-state residency numbers results in the considerable power savings illustrated in (Figure 6) . A 100-percent C4 state residency is not achievable because of certain break events such as interrupts, wake up events caused by drivers, or because of the polling architecture of USB devices.

Figure 7: C-state residency

Power savings on Sysmark 2007 on a suite-by-suite basis and on average are illustrated in (Figure 8) , which shows a 5-percent improvement in AC platform power on average for the 2008 platform. Average here is the arithmetic mean of the power consumed by each component of the benchmark.

Figure 8: Sysmark power savings

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