Civil Rights
Movements, leaders, victories and the continuing fight for equality.
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Explore the people, places, events, achievements, struggles and stories that shaped our journey.
Movements, leaders, victories and the continuing fight for equality.
Innovation, patents, science, technology and world-changing contributions.
Pioneers, champions, Negro Leagues, records, activism and excellence.
Meet the people whose lives, choices and achievements shaped the journey.
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Moments that changed communities, movements, institutions and the nation.
Wilmington, North Carolina once had a thriving Black middle class and an elected interracial government. In 1898 white supremacists used violence to overthrow that government, kill Black residents and drive many others from the city.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
In computing and in embedded systems, a programmable interval timer (PIT) is a counter that generates an output signal when it reaches a programmed count. The output signal may trigger an interrupt.
PITs may be one-shot or periodic. One-shot timers will signal only once and then stop counting. Periodic timers signal every time they reach a specific value and then restart, thus producing a signal at periodic intervals. Periodic timers are typically used to invoke activities that must be performed at regular intervals.
Counters are usually programmed with fixed intervals that determine how long the counter will count before it will output a signal.
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. Timer 0 is used by Microsoft Windows (uniprocessor) and Linux as a system timer, timer 1 was historically used for dynamic random-access memory refreshes and timer 2 for the PC speaker.[2]
The LAPIC in newer Intel systems offers a higher-resolution (one microsecond) timer.[3] This is used in preference to the PIT timer in Linux kernels starting with 2.6.18.[4]
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
In computing and in embedded systems, a programmable interval timer (PIT) is a counter that generates an output signal when it reaches a programmed count. The output signal may trigger an interrupt.
The High Precision Event Timer (HPET) is a hardware timer available in modern x86-compatible personal computers. Compared to older types of timers available in the x86 architecture, HPET allows more efficient processing of highly timing-sensitive applications, such as multimedia playback and OS task switching. It was developed jointly by Intel and Microsoft and has been incorporated in PC chipsets since 2005. Formerly referred to by Intel as a Multimedia Timer, the term HPET was selected to avoid confusion with the software multimedia timers introduced in the MultiMedia Extensions to Windows 3.0. Older operating systems that do not support a hardware HPET device can only use older timing facilities, such as the programmable interval timer (PIT) or the real-time clock (RTC). Windows XP, when fitted with the latest hardware abstraction layer (HAL), can also use the processor's Time Stamp Counter (TSC), or ACPI Power Management Timer (ACPI PMTIMER), together with the RTC to provide operating system features that would, in later Windows versions, be provided by the HPET hardware. Confusingly, such Windows XP systems quote "HPET" connectivity in the device driver manager even though the Intel HPET device is not being used.
The 6532 RAM-I/O-Timer (RIOT) was an integrated circuit made by MOS Technology, as well as second sources such as Rockwell. It incorporates 128 bytes of static RAM, two bidirectional 8-bit digital input/output ports, and an 8-bit Programmable interval timer (with pre-divider). This high degree of integration made it popular in the late 1970s and early 1980s, as it could take the place of several different integrated circuits (ICs). It is used in the Atari 2600 video game console. The chip was also deployed in Gottlieb pinball machines, such as Haunted House and Black Hole, the Atari 810 and 1050 disk drives, as well as Commodore's 8050, 8250 & 8250LP PET disk drives. The Atari 850 Interface, which gives the Atari 400 and 800 computers an RS-232 interface, uses two 6532 chips. 6532 ICs were available in 1 MHz and 2 MHz versions. The form factor was a 40-pin ceramic or plastic DIP package.
A PC speaker is a loudspeaker built into some IBM PC compatible computers. The first IBM Personal Computer, model 5150, employed a standard 2.25-inch (57 mm) magnetic driven (dynamic) speaker. More recent computers use a tiny moving-iron or piezo speaker instead. A PC speaker generates waveforms using the programmable interval timer, an Intel 8253 or 8254 chip. The speaker allows software and firmware to provide auditory feedback to a user, such as to report a hardware fault.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Brown v. Board of Education in 1954.
