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This frequency, divided by 2 16 (the largest divisor the 8253 is capable of) produces the ≈18.2 Hz timer interrupt used in MS-DOS and related operating systems. In the original IBM PCs, Counter 0 is used to generate a timekeeping interrupt. Counter 1 is used to trigger the refresh of DRAM memory. Counter 2 is used to generate tones via the PC ...
The Intel 8253 PIT was the original timing device used on IBM PC compatibles. It used a 1.193182 MHz clock signal (one third of the color burst frequency used by NTSC, one twelfth of the system clock crystal oscillator, [1] therefore one quarter of the 4.77 MHz CPU clock) and contains three timers.
The clock rate of the PC's programmable interval timer which drives the speaker is fixed at 1,193,180 Hz, [3] and the product of the audio sample rate times the maximum DAC value must equal this. Typically, a 6-bit DAC [8] with a maximum value of 63 is used at a sample rate of 18,939.4 Hz, producing poor but recognizable audio. [9]
The aperiodic interrupts offered by the APIC timer are used by the Linux kernel tickless kernel feature. This optional but default feature is new with 2.6.18. When enabled on a computer with an APIC timer, the kernel does not use the 8253 programmable interval timer for timekeeping. [12]
The references to two timers is not true. In Intel ICH4 documentation, the timer exists in IO ports 40h..43h, and the same timer is aliased to IO ports 50h..53h for some reason. A very good guess would be that the original IBM PC had it like this too to simplify IO address decoding, but this is just a guess.
A tickless kernel is an operating system kernel in which timer interrupts do not occur at regular intervals, but are only delivered as required. [1]The Linux kernel on s390 from 2.6.6 [2] and on i386 from release 2.6.21 [3] can be configured to turn the timer tick off (tickless or dynamic tick) for idle CPUs using CONFIG_NO_HZ, and from 3.10 with CONFIG_NO_HZ_IDLE extended for non-idle ...
Crystal oscillators can be manufactured for oscillation over a wide range of frequencies, from a few kilohertz up to several hundred megahertz.Many applications call for a crystal oscillator frequency conveniently related to some other desired frequency, so hundreds of standard crystal frequencies are made in large quantities and stocked by electronics distributors.
On March 6, 2000, AMD demonstrated passing the 1 GHz milestone a few days ahead of Intel shipping 1 GHz in systems. In 2002, an Intel Pentium 4 model was introduced as the first CPU with a clock rate of 3 GHz (three billion cycles per second corresponding to ~ 0.33 nanoseconds per cycle). Since then, the clock rate of production processors has ...