WITH EACH successive technology generation, process and environmental variations consume an increasingly large portion of the microprocessor design envelope. Today's microprocessors are limited not only by raw circuit performance but also by power consumption, process variability, cooling capacity, and long-term device reliability. Each market segment requires a different combination of features and power consumption. To further complicate the design space, process technology is not static, and significant process advances occur throughout a product's lifetime. Traditional techniques for minimizing design exposure to process and environmental variations are quickly becoming difficult to implement. A common method for matching circuits (for example, in a clock distribution) is to use wide wires and long-channel devices. Modern process technologies severely limit wire dimensions to maintain wire uniformity. Long-channel devices come with many problems, including slow performance, inadequate modeling, and poor scaling compared to the more common short devices.
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