Stepping (microprocessors)

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The term stepping ( stɛping ) - also called core revision at AMD - describes successive versions of a processor of the same processor type in microprocessors . Stepping is the most precise description of a processor type or the version of a processor type that is visible to the consumer. There can be several stepping versions within a processor generation.

background

While new processor types within a processor series usually change basic processor data that are meaningful for the user (e.g. clock frequency , instruction set , number and type of processing units , thermal power dissipation ), only internal details are usually changed when stepping is changed , however, the main features of the processor remain unchanged.

The stepping can also be the name of the exposure mask (s) used in production, but this is rarely known exactly outside the manufacturer.

For example, when the stepping is changed, errors can be eliminated, changes in the manufacturing process such as reducing the structure width or measures that improve the production yield can be implemented. These changes are not visible to the user. Sometimes new interfaces or internal functions are added with a stepping process; this is usually done in anticipation of the next generation of processors. What all steppings have in common, however, is that processors of the same type but different steppings are in principle interchangeable within the specified operating parameters. However, by eliminating errors, this does not apply without restriction: Errors in certain steppings can require appropriate countermeasures in the system (especially on the software side), so that stepping backwards could be associated with difficulties if the countermeasures are not implemented. Some errors cause a restriction compared to the originally specified operating parameters (for example the clock frequency) that were only achieved with later stepping, so that compromises can also be made here in terms of interchangeability.

It also happens that different simultaneously available processor types from the same processor family have the same stepping. This can indicate that these processors are manufactured in the same manufacturing process with the same exposure masks, are checked for performance or other properties such as defective computing units after production and are then sold as different processor types. For example, a processor in a family that is available as both a single core processor and a multi-core processor could always be made with four cores. After production, the individual dies are checked for the number of functional cores. Those with four functional cores are sold as four-core processors, those with two or three functional cores as two-core processors or possibly three-core processors (e.g. with AMD's K10 generation) and those with one functional core as single-core processors, although all processors in this family were originally manufactured with four cores were. Likewise, after production, copies of a processor can be checked for the maximum clock frequency with which they can be operated safely (due to manufacturing deviations, this can vary between individual copies from the same production line) and then sold with this determined maximum clock frequency. Such a procedure lowers the production costs, since only one production line is used, and increases the yield because partly defective or not fully efficient copies can be sold anyway.

For users who want to overclock their processors , differences between the individual steppings are often discussed in forums, and certain steppings that have been identified as particularly well overclockable through tests are preferred within these user groups. However, it cannot be statistically proven whether a discussed stepping “X” can really be overclocked better than stepping “Y”, since important background information is usually missing from the manufacturer.

literature

  • Benjamin Benz: Pin-Wald versus Pad-Wiese - Signposts through the x86 processor jungle In: c't , No. 7, 2008, page 178ff.

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