Core tension

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In electronics and information technology, a supply voltage for an integrated circuit (for example a microprocessor ) is referred to as core voltage , or V core or core voltage . The term is used to differentiate when a component has a different supply voltage for communication with the outside world, the latter being referred to as I / O voltage.

The technical background is the independent determination of the supply voltage of the actual inner workings (e.g. the eponymous processor core), which is a decisive parameter for the maximum clock rate (speed), but also the power loss (heat generation) of the component, and the Voltage for the I / O connections, which determines the logic level at the module connections and thus ensures compatibility with other connected modules. Level converters , which convert the signal voltages between the core voltage level and the I / O voltage level , are part of the module's I / O circuit . By separating the two supply voltages, comparatively low core voltages are possible, which is a prerequisite for the performance of modern microprocessors or FPGAs , for example . It is also possible to design the core voltage variably in order to adapt its level to the changing demand for computing power. (An example here is increasing the battery life of a cell phone or laptop .)

Analogous to this separation between the core and the outside world, different system parts within a module (e.g. CPU core, memory and peripheral areas of a microcontroller ) can be operated with a supply voltage adapted to their needs, so that such a module can then have three or more even more voltages are required for operation. These do not even have to be of different levels - there is often only a separation so that individual function blocks can be switched off independently of the others. Another reason for separate supply of individual function blocks is to reduce mutual interference - often found in analog-to-digital or digital-to-analog converters as separate supplies for the analog and digital sections. In this context, however, one does not speak of nuclear stress.

Details

The height of the core tension is specified by the manufacturer. A nominal voltage is specified that must be adhered to with a specified tolerance . Alternatively, a range can also be specified, possibly also depending on other parameters (e.g. ambient temperature , clock rate).

One difficulty in supplying a processor, for example, is that the current consumption fluctuates sharply in a very short time (up to several hundred amperes per microsecond). Appropriate measures (e.g. buffer capacitors ) must be used to absorb the resulting voltage fluctuations so that the core voltage remains within the specified (tolerance) range. Otherwise, stable operation of the processor can usually no longer be guaranteed.

In the course of optimizing for the lowest possible consumption, the core voltage plays an important role: Today, many CPU architectures are able to adapt the clock frequency and voltage to the load on the functional units during operation (see Undervolting ). This has positive effects on energy consumption and - indirectly - on heat loss. This leads to a longer runtime, especially with mobile devices, or the devices can get by with smaller and lighter power sources ( batteries ).

Since the stability and efficiency of a CPU depend heavily on the quality of the power supply, manufacturers issue strict guidelines for voltages, tolerances and other properties (e.g. type and number of energy-saving mechanisms ). For current CPUs with x86 - architecture , these for example in the ATX12V specification (→ ATX format held).

Current developments show that the term "core voltage" may no longer be applicable in the future: A further improvement in energy efficiency lies in the independent supply of the individual functional units of a CPU with the optimal clock frequency and voltage. There is then no longer any core tension in the classic sense.

Importance of core voltage in overclocking

With the proliferation of computer games and related hardware, so-called overclocking also came into fashion. If a CPU is operated outside of the specified parameters, for example in order to achieve an increase in performance through a higher clock frequency, the current differences are even higher and the supply voltage may briefly drop so far that stable operation is impossible. Raising the core voltage can counteract this, but usually leads to an increase in the heat loss - this may then have to be dissipated by additional measures.

literature

  • Klaus Wüst: Microprocessor technology. 3rd edition, Vieweg + Teubner, Wiesbaden 2009, ISBN 978-3-8348-0461-7 .
  • Peter Fischer-Stabel, Klaus-Uwe Gollmer: Computer science for engineers. Fit for the Internet of Things, UVK Verlagsgesellschaft mbH, Konstanz and Munich 2016, ISBN 978-3-8252-4645-7 .

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