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As with any fabrication process, the actual quality of each unit in production can vary under the influence of numerous variables, both internal and external. For example, consider automobile manufacturing. Thousands of vehicles are manufactured during every production year. One individual vehicle may outperform another of the same make and model simply because no two cars rolling off the assembly line are exactly the same.
Assembly lines operate within tolerances. Designers set base specifications that represent a minimum standard of quality before the product can be sold in the retail market. Let's take the automotive industry example to the next level. Assume that each vehicle within a given model line must perform at a specific minimum miles-per-hour rating before being released for retail consumption. Imagine that a speed limit of 100 miles per hour is such a minimum. In order to test the production quality, designers could sample two individual vehicles of the same model manufactured on different days. Vehicle A reaches maximum performance at 100 mph, so the designers are satisfied. Vehicle B offers even better performance, reaching 105 mph during testing. While both vehicles were produced at the same plant with the same materials, small differences between them can result from even smaller variances in the manufacturing process.
Most computer processor manufacturers use more exacting tolerances than those illustrated in the automobile example, though the general analogy holds. Because the average processor is comprised of millions of microscopic transistor circuits, the possibility for variances is considerable. For example, each speed grade of the Athlon XP processor from AMD is fabricated to essentially the same expected tolerances. Minor fabrication differences among units may lead one processor to reach a maximum stable operational speed of 1.4 GHz, while another chip of the same design may operate at 1.6 GHz.
Automobile companies sell all comparably equipped vehicles of a particular model at the same base price, while a processor company can choose to sell the better performing chip at a higher price to maximize profit yields with lower capital costs. If the automobile manufacturer in the above example operated like a processor manufacturer, it would sell the car that reached 100 mph at one price and the car that reached 105 mph at a higher price, even though both vehicles were essentially identical in every other respect. Conversely, a processor manufacturer like AMD could behave like an automobile maker, offering each CPU without any performance rating beyond the flat minimum speed requirement. This marketing strategy would yield the same base revenue for all processors. Profits would decline due to the standard economies of supply and demand.
Offering varying speed grades of the same product means maximizing profit. Most computer users exhibit a consistent desire for better performance, whether they need it or not. Computer performance is dictated by megahertz ratings, assuming all other subsystem characteristics are identical. Most buyers equate MHz ratings to performance, though many other aspects of processor design contribute to performance. The cost of acquiring higher MHz models can prove limiting, which leads some consumers to investigate the benefits of overclocking.
Popular fabricators and chip suppliers like Intel and UMC produce millions of circuit-based devices each year. The trend toward bulk fabrication techniques leads to a practice known as speed binning, which allows the computer industry to differentiate cost and performance characteristics while protecting profits. Still, the sheer number of chips being produced each year prevents manufacturers from testing every individual processor for its maximum operating speed potential.
In Speed Binning, the manufacturer selects processors from a given production batch and puts those processors through reliability testing to determine the maximum reliable speed that is common to all processors in that batch. The processors in the batch are then usually marked for sale at the speed rating determined in the testing process.
Even though speed binning is a well-developed and highly efficient process, quality variances still exist among processors in any given batch. These variances often allow processors to be overclocked beyond their rated speed, since the speed rating for any given batch must be such that all processors in the batch can operate at the speed rating, even though each and every individual processor is not speed tested.
Speed binning produces unique benefits for both manufacturers and consumers. Manufacturers can charge higher selling prices for better performing processors. Consumers can opt for lower speed grades to minimize costs, while enthusiasts among them may obtain an even greater performance-to-price ratio if they are willing to push the stability envelope and overclock their processors.
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