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A memory-mapped file is a segment of virtual memory [1] that has been assigned a direct byte-for-byte correlation with some portion of a file or file-like resource. This resource is typically a file that is physically present on disk, but can also be a device, shared memory object, or other resource that an operating system can reference through a file descriptor.
A portion of the computer's hard drive is set aside for a paging file or a scratch partition, and the combination of physical RAM and the paging file form the system's total memory. (For example, if a computer has 2 GB (1024 3 B) of RAM and a 1 GB page file, the operating system has 3 GB total memory available to it.)
The minimum cache size is 250 MB. In Vista or with FAT32 formatting of the drive, the maximum is 4 GB. In Windows 7 or later with NTFS or exFAT formatting, the maximum cache size is 32 GB per device. Windows Vista allows only one device to be used, while Windows 7 allows multiple caches, one per device, up to a total of 256 GB. [5]
The CAS signal is only needed to enable the output (the data out pins were held at high-Z while CAS was deasserted), so time from CAS assertion to data valid (t CAC) is greatly reduced. [63] Fast page mode DRAM was introduced in 1986 and was used with the Intel 80486.
One manifestation of data degradation is when one or a few bits are randomly flipped over a long period of time. [14] This is illustrated by several digital images below, all consisting of 326,272 bits. The original photo is displayed first. In the next image, a single bit was changed from 0 to 1. In the next two images, two and three bits were ...
In Mac OS X (versions 10.0.x through 10.4.x) UDF-formatting of DVD-RAM is no longer supported, instead formatting and writing DVD-RAM is done in HFS+ format. (UDF support was re-implemented in 10.5 Leopard) (HFS and UFS should also be supported on older versions of Mac OS X that retain support for these file systems.) [ 10 ] [ 11 ]
The time to read the first bit of memory from a DRAM without an active row is T RCD + CL. Row Precharge Time T RP: The minimum number of clock cycles required between issuing the precharge command and opening the next row. The time to read the first bit of memory from a DRAM with the wrong row open is T RP + T RCD + CL. Row Active Time T RAS
Non-volatile random-access memory (NVRAM) is random-access memory that retains data without applied power. This is in contrast to dynamic random-access memory (DRAM) and static random-access memory (SRAM), which both maintain data only for as long as power is applied, or forms of sequential-access memory such as magnetic tape, which cannot be randomly accessed but which retains data ...