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LongRun2 Technology offers a versatile solution for both the increasing leakage power problems and yield loss due to expanding process variations. It is also highly compatible and synergistic with many other power reduction approaches used by the industry. Below are described some other common techniques to illustrate how LongRun2 Technology are compatible with, and provides additional benefits beyond, those conventional techniques.
Clock Gating |
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Power Gating |
Clock gating is a popular technique used to reduce active power in a system in which clocks are turned off from logic blocks that are not in use. While clock gating is an effective technique. Logic blocks with clocks disabled will still dissipate leakage power, which can be substantial in 90nm, 65nm and finer geometries. Furthermore, clock gating cannot compensate for the expanding process variations in 90nm, 65nm and finer geometries. LongRun2 complements clock gating by helping reduce active power and narrowing process variation.
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One way to minimize power beyond merely clock gating is to turn off power to a logic block when not being used (also referred to "Power Shut Off" or "sleep transistors"). By effectively removing the supply voltage when idle, a logic block contributes very little leakage power. Similar to clock gating, there are several engineering challenges that need to be addressed before Power Gating can be used. The design must be carefully partitioned to identify which sections can be turned off and when. Proper timing must be maintained so that the blocks are powered up when needed, which complicates the timing analysis. Finally, additional transistors are needed to gate the power supply, which introduces area and performance trade-offs. LongRun2 offers a more straightforward approach to reducing leakage, simplifies timing analysis, and also offers distribution tightening benefits that Power Gating lacks.
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Multiple Threshold Voltage Transistors ("Multi-Vt") |
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Traditional Body Bias without LongRun2 |
| Semiconductor designers sometimes use different threshold voltage transistors for different logic blocks and logic gates within a device. Typically low threshold voltage, high leakage transistors are used for critical paths where performance is a requirement and high threshold voltage transistors are used in less critical paths. This technique can be effective for a design with pronounced critical paths. Also, Multi-Vt does little to target process variation except reducing the use of Low-Vt transistors to key areas. LongRun2 is a complementary technique that can work in conjunction with or instead of Multi-Vt while also adding additional distribution tightening benefits. |
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A traditional body bias solution can provide some of the advantages of LongRun2 Technology, however, LongRun2 adds valuable tools and technologies to make body bias more practical to use. LongRun2 also offers innovations in dynamic bias control, feedback and optimization, as well as supporting circuit structures and control techniques that may help reduce minimum operating voltage. |
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