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In operating systems that use virtual memory, every process is given the impression that it is working with large, contiguous sections of memory. In reality, each process' memory may be dispersed across different areas of physical memory, or may have been moved (paged out) to another storage, typically to a hard disk.

When a process requests access to a data in its memory, it is the responsibility of the operating system to map the virtual address provided by the process to the physical address of the actual memory where that data is stored. The page table is where the operating system stores its mappings of virtual addresses to physical addresses, with each mapping also known as apage table entry (PTE).

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efore the arrival of Spanish conquistadores, different tribes like Huarpes, Diaguitas, Capazanes, Olongastas and Yacampis, highly influenced by the Inca empire, inhabited the area.

The city of San Juan de la Frontera was founded by Juan Jufré y Montesa in 1562 and relocated 2 kilometres south in 1593 due to the frequent flooding of the San Juan River.

In 1776, San Juan was annexed to the Viceroyalty of the Río de la Plata, becoming one of the cities of the Province of Cuyo. In the same year, the first recorded earthquake caused massive damage to the city.

The father of Argentine independence, Gen. Jose de San Martin, was appointed Governor of the Province of Cuyo in 1814. From there, San Martin began his legendary crossing of the Andes, one of military history's great tactical decisions. San Juan, then a small town, was a great supporter of the expedition supplying gold, men and mules.

In 1820, San Juan was granted autonomy from the Province of Cuyo, thereby becoming an autonomous province. The remainder of Cuyo region became Mendoza Province.

Following an era of international isolation for Argentina, the advent of new, more liberal government in 1853 attracted a number of exiled intellectuals back into San Juan. Among these, was a San Juan military officer and novelist named Domingo Sarmiento. Sarmiento was eventually elected governor in 1862, pursuing sorely needed public investments and enacting Argentina's first law mandating compulsory education (at that time about 80% of the adult population lacked any form of education). Once elected President of Argentina in 1868, those policies became national law.

In 1944 a moderate, yet highly destructive earthquake near the capital destroyed most of the city and killed 10,000 people. A fundraiser was organized to raise money for the victims of the quake where Colonel Juan Perón met his eventual wife and political companion Eva Duarte.

A more powerful earthquake stuck the same city in 1977; however new construction codes put in effect following the 1944 incident kept damage to a relative minimum. The most noteworthy loss following this event was the destruction of the Cathedral of San Juan (image, at top). A new, modernist house of worship was quickly put up in its place and inaugurated in 1979.

Among the most rapidly growing provinces in Argentina after 1945, the national government began the construction of the National University of San Juan, which opened its doors in 1973. Congress further responded to the needs of San Juan's growing agricultural sector by breaking ground in the mid '70s for the largest hydrostructural project in the province up to that point, the Ullum Dam and Reservoir. Inaugurated in 1980, it has contributed to the province's production of irrigated desert crops, like olives, figs and, most importantly, wine grapes.

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Write combining (WC^[1]) is a computer bus technique for allowing data to be combined and temporarily stored in a buffer — the write combine buffer (WCB) — to be released together later in burst mode instead of writing (immediately) as single bits or small chunks.

Write combining cannot be used for general memory access (data or code regions) due to the weak ordering. Write-combining does not guarantee that the combination of writes and reads is done in the expected order. For example, a Write/Read/Write combination to a specific address would lead to the write combining order of Read/Write/Write which can lead to obtaining wrong values with the first read (which potentially relies on the write before).

In order to avoid the problem of read/write order described above, the write buffer can be treated as a fully associative cache and added into the memory hierarchy of the device in which it is implemented.^[2] Adding complexity slows down the memory hierarchy so this technique is often only used for memory which does not need strong ordering (always correct) like the frame buffers of video cards.