Memory Barriers
Memory-mapped I/O is the cause of memory barriers in older generations of computers. The 640 KiB barrier is due to the IBM PC placing the Upper Memory Area in the 640–1024 KiB range (of its 20-bit memory addressing).
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Famous quotes containing the words memory and/or barriers:
““I have done it,” says my memory. “I cannot have done it,” says my pride, refusing to budge. In the end—my memory yields.”
—Friedrich Nietzsche (1844–1900)
“In America the majority raises formidable barriers around the liberty of opinion; within these barriers an author may write what he pleases, but woe to him if he goes beyond them.”
—Alexis de Tocqueville (1805–1859)