Memory controller: Difference between revisions

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[[File:Intel_82PM45_Memory_Controller_Hub_-_MCH_AC82PM45-SLB97_-3718.jpg | thumb|right | Intel 82PM45 Memory Controller Hub]]

A '''memory controller''', also known as '''memory chip controller''' ('''MCC''') or a '''memory controller unit''' ('''MCU'''), is a digital circuit that manages the flow of data going to and from a computer's [[main memory]].<ref>Comptia A+ Certification Exam Guide, Seventh Edition, by Mike Meyers, in the glossary, bottom of page 1278: "Chip that handles memory requests from the CPU."</ref><ref>{{cite book |last1=Neat |first1=Adam G. |url=https://books.google.com/books?id=PJ49xcoRb1QC&q=%22memory+controller+unit%22&pg=PA100 |title=Maximizing Performance and Scalability with IBM WebSphere |date=2003-12-04 |publisher=Apress |isbn=9781590591307 |access-date=6 February 2015}}</ref> When a memory controller is integrated into another chip, such as an integral part of a [[microprocessor]], it is usually called an '''integrated memory controller''' ('''IMC''')....

Memory controllers contain the logic necessary to read and write to [[dynamic random-access memory]] (DRAM), and to provide the critical [[memory refresh]] and other functions. Reading and writing to DRAM is performed by selecting the row and column data addresses of the DRAM as the inputs to the [[multiplexer]] circuit, where the [[demultiplexer]] on the DRAM uses the converted inputs to select the correct memory ___location and return the data, which is then passed back through a multiplexer to consolidate the data in order to reduce the required [[Bus (computing)|bus]] width for the operation. Memory controllers' bus widths range from [[8-bit]] in earlier systems, to 512-bit in more complicated systems, where they are typically implemented as four [[64-bit]] simultaneous memory controllers operating in parallel, though some operate with two 64-bit memory controllers being used to access a [[128-bit]] memory device.

Some memory controllers, such as the one integrated into [[PowerQUICC]] II processors, include [[error detection and correction]] hardware.<ref>[http://www.freescale.com/files/training_pdf/24815_PQ2_MEM_CONTROL_WBT.pdf "Memory Controller"]</ref> Many modern processors are also integrated [[memory management unit]] (MMU), which in many [[operating system]]s implements [[virtual addressing]]. On early x86-32 processors, the MMU is integrated in the CPU, but the memory controller is usually part of [[northbridge (computing)|northbridge]].<ref>https://vikramuniv.ac.in/files/academic/e-Resources2020-21/engg2020-21/BE_6_SEM_EE_MP_MC-_COMP._OF_8086_FAMILY-AMIT_THAKUR-converted-converted.pdf</ref>..

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