What is GigaHertz (GHz) or MegaHertz (MHz) ? Clock Rate

The clock rate typically refers to the frequency at which a chip like a central processing unit (CPU), one core of a multi-core processor, is running and is used as an indicator of the processor's speed. It is measured in clock cycles per second or its equivalent, the SI unit hertz (Hz).

The clock rate of the first generation of computers was measured in hertz or kilohertz (kHz), but in the 21st century the speed of modern CPUs is commonly advertised in GigaHertz (GHz).

This metric is most useful when comparing processors within the same family, holding constant other features that may impact performance. Video card and CPU manufacturers commonly select their highest performing units from a manufacturing batch and set their maximum clock rate higher, fetching a higher price.

Definition of MHz, GHz

(MegaHertZ) One million cycles per second. It is used to measure the transmission speed of electronic devices, including channels, buses and the computer's internal clock. A one-megahertz clock (1 MHz) means some number of bits (1, 4, 8, 16, 32 or 64) can be manipulated at least one million times per second. A two-gigahertz clock (2 GHz) means at least two billion times. The "at least" is because multiple operations often occur in one clock cycle.

Both megahertz (MHz) and gigahertz (GHz) are used to measure CPU speed. For example, a 1.6 GHz computer processes data internally (calculates, compares, copies) twice as fast as an 800 MHz machine.

Why Isn't It Faster?

A CPU in the new computer billed as two times faster than the old computer does not mean twice as much finished work gets done in the same time frame. Internal cache design, bus speed, disk speed and network speed all contribute to the computer's actual processing speed and performance (the overall throughput).

Users are often dismayed to find only incremental improvements after purchasing a so-called "faster" computer. In addition, newer versions of software are sometimes slower than previous versions, and a faster computer is often required just to maintain the same performance level as the old software.

MHz and GHz Are the Heartbeat

When referencing CPU speed, the megahertz and gigahertz ratings are really the heartbeat of the computer, providing the raw, steady pulses that energize the circuits. If you know German, it is easy to remember. The word "Herz," pronounced "Hayrtz" means heart. This was a coincidence, because in 1883, Heinrich Hertz identified electromagnetic waves.

Differences between MHz and GHz

One GHz equals one billion cycles per second whereas one MHz equals one million cycles per second. (while writing this post)

The Fastest Phone is the 6 GB of RAM wielding OnePlus 3 equipped with a quad-core Snapdragon 820, with two cores clocked at 2.2 GHz and the other two at 1.6 GHz.

The fastest Laptop CPU is the Intel Core i7-6700K Sporting base clock rate of 4GHz, with a rather meager maximum Turbo Boost of 4.2GHz.

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