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The quartz movement in battery-powered watches is plated with gold and trimmed individually using laser to achieve a vibration frequency of exactly 32,768 Hz to keep time accurately.

The crankshaft in pistol engine is adjusted by hand or computer to make sure the center of gravity is in the middle of the shaft for smooth rotation.

The 50 ohms resistors on an impedance standard substrate for high frequency measurements are laser trimmed as well for ultimate accuracy.

Therefore, does each individual CPU get calibrated by any means before being shipped? I would imagine the answer to be yes as CPUs are intricate products that should require some tweaking. But how is CPU calibration done on a hardware level?

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    \$\begingroup\$ Individual CPUs are "binned" based on their performance and might have optional or redundant blocks that can be switched off, but this is not a calibration process. High-end CPU fabrication is probably the most intensively calibrated and precise mass production process in the world, but it is the process that needs to be nearly perfect, not the individual CPU. \$\endgroup\$ – jbarlow Jul 23 '16 at 5:56
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In a CPU per se, no part requires calibration. Pure digital logic does not need it. In a microcontroller (combination of CPU+periperals in a single chip), the only parts that would need calibration would be the internal oscillators, and eventually a few specific elements for particular peripherals (internal references for ADC/DAC, maybe some internal termination resistors for USB, ...). But this depends on the microcontroller capabilities.

If calibration is required, it is done directly on the wafer during production. Once the chips are made, some probes measure the elements needing calibration (e.g specific resistors, RC network frequency, reference voltage, ...) and either adjust their value using laser trimming, or, in some cases, just store the value read in some part of EEPROM, for later use by the firmware.

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MCUs that have internal RC oscillators are typically calibrated by storing a number in non-volatile memory that trims the oscillator frequency. That number might be used directly, but more often it is loaded into a register to trim the hardware oscillator.

The calibration is done in testing.

As a rough example, the total range (hardware limited) might be something like 25% and the center point (and range) chosen so that virtually all processors can be tuned to close to the desired frequency. Some processors might be toward one or the other extreme depending on manufacturing tolerances.

Similar methods exist for calibration voltage sources etc., not always with visible (to the programmer) methods.

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The simple and basic answer is no. There is typically nothing inside a CPU chip that requires any kind of "calibration". CPU chips are certainly tested to confirm they operate properly. And many are "graded" for speed and/or other operational parameters.

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