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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 ...
The Time Stamp Counter was once a high-resolution, low-overhead way for a program to get CPU timing information. With the advent of multi-core/hyper-threaded CPUs, systems with multiple CPUs, and hibernating operating systems, the TSC cannot be relied upon to provide accurate results — unless great care is taken to correct the possible flaws: rate of tick and whether all cores (processors ...
Download QR code; In other projects ... English: Intel 8253 and Intel 8254 Programable Interval Timers. ... You are free: to share – to copy ...