Microprocessor frequency, also called clock rate or clock speed, specifies internal frequency of CPU cores. The higher the frequency is for a given CPU architecture, the faster the processor is. Processor frequency is not the only parameter that affects system performance. Another parameter than greatly affects the performance is CPU efficiency, that is how many Instructions Per Clock (IPC) the CPU can process. Knowing these two parameters it's easy to calculate total number of instructions per second that can be processed by CPU: Frequency x IPC. Most modern AMD and Intel microprocessors tried to improve their performance by improving their IPC, and, whenever possible, by increasing clock rate. Intel Netburst microarchitecture used quite different approach - it tried to increase operating frequency at the expense of IPC. This didn't work well for this microarchitecture.
Modern microprocessors do not always operate at the same clock speed. To lower power consumption and/or lower package temperature, all processors with PowerNow!, Pure Power or Enhanced SpeedStep technology may temporarily reduce their operating frequency. Many modern processors also utilize frequency boost technologies, such as Precision Boost or Turbo Boost, to temporarily increase processor performance by increasing clock rate above nominal clock rate.
The CPU frequency is measured in Hertz. The frequency can also be expressed in:
- Kilohertz, or
kHz , equals to 1,000 Herts - Megahertz, or MHz, equals to 1,000,000 Herts or 1,000
kHz - Gigahertz, or GHz, equals to 1,000,000,000 Herts, or 1,000,000
kHz , or 1,000 MHz.
First microprocessors ran at frequencies close to 1 MHz. Modern microprocessors run at frequencies exceeding 1 GHz, or 1,000,000,000 Hertz.