Source: Tom's Guide US | Keywords: 4x4 | Themes: Business Notebooks
- 1. P4-M: The CPU For The Full-Sized Consumer Notebook
- 2. Compared: 1.4, 1.7, 1.8 And 2.2 GHz Mobile Pentium 4-M Vs. Desktop CPU
- 3. Pentium 4-M Consumption Modes: What's Behind TDP & Co
- 4. Energy-Saving Technologies In The Pentium 4-M: Enhanced Speedstep, Deeper Sleep & IMVP
- 5. Why Does The P4-M Permit A Higher Maximum Junction Termperature?
- 6. The Test System: Asus L3C
- 7. Benchmarks Under Windows XP
- 8. Synthetic Benchmarks
- 9. Multimedia Performance: PC Mark 2002
- 10. Video Encoding With Virtual Dub 1.4.1
- 11. File Compression: Winace 2.2
- 12. Open GL Games: Quake3 Arena
- 13. System Performance: Sysmark 2002
- 14. Battery Tests - Run-Down Times For Games, Presentations And DVD Playback
- 15. Conclusion: High Clock Speed Is Not Always The Best Choice
- 16. More on this topic
4. Energy-Saving Technologies In The Pentium 4-M: Enhanced Speedstep, Deeper Sleep & IMVP
The energy-saving technology "Enhanced Speedstep" is the practical implementation of the inherent physical laws described above: the Pentium 4-M can be switched between two power states in real time depending on the processor throughput needed by an application. In Maximum Performance mode, the CPU runs at maximum speed and at a higher core voltage of 1.3 V; in Battery Optimized mode, the core frequency for all Pentium 4-M models is 1.2 GHz and the voltage is lowered to 1.2 V.
The switch between the two operating states, as already mentioned, is made completely automatically. In Windows XP, the user can also deactivate the option and manually tweak CPU performance.
| Windows XP Power Schemes | AC Power (Frequency Example mobile Pentium-4-M 2.2 GHz) | Battery DC (Frequency Example mobile Pentium-4-M 2.2 GHz) |
|---|---|---|
| Home/Office Desktop | None (2.2 GHz Always) | Adaptive (1.2 GHz <->2.2 GHz) |
| Portable /Laptop | Adaptive (1.2 GHz <->2.2 GHz) | Adaptive (1.2 GHz <->2.2 GHz) |
| Presentation | Adaptive (1.2 GHz <->2.2 GHz) | Degrade (1.2 GHz) |
| Always On | None (2.2 GHz Always) | None (2.2 GHz Always) |
| Minimal Power Management | Adaptive (1.2 GHz <->2.2 GHz) | Adaptive (1.2 GHz <->2.2 GHz) |
| Maximum Battery | Adaptive (1.2 GHz <->2.2 GHz) | Degrade (1.2 GHz) |
The choice of power scheme in the control panel determines the CPU's performance properties.
While energy consumption is lowest for the Pentium 4 in its Deep Sleep Status processor mode, the Pentium 4-M has an additional sleep mode that uses even less energy, the Deeper Sleep mode . In this mode, the CPU operates on a voltage of just 1.0 V; the processor clock speed, as in Deep Sleep mode, is no longer relevant. The switch from Deep to Deeper Sleep is made within a few hundred microseconds. This enables the CPU to use even brief times of inactivity - for example, the time between two keystrokes - to switch to this mode and save energy.
The least known energy-saving technology is I.M.V.P. This acronym is short for Intel Mobile Voltage Positioning. A diagram best explains how IMVP works.
Usually, the voltage regulators that deliver the supply voltage for the CPU work statically, i.e., the supply voltage VCC remains constant within a tolerance zone, regardless of processor load.
The CPU's load curve with a static voltage regulator.
With an IMVP regulator, the supply voltage Vcc is lowered in step with a rising processor load.
The CPU's load curve with IMVP voltage regulator.
This measure produces lower CPU power consumption relative to a growing processor load. Thus, a notebook system with an IMVP regulator also has a lower TDP, average and active power, compared with a system that has only one statically functioning voltage regulator.
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