Memory data register

The Memory Data Register (MDR) is the register of a computer's control unit that contains the data to be stored in the computer storage (e.g. RAM), or the data after a fetch from the computer storage. It acts like a buffer and holds anything that is copied from the memory ready for the processor to use it.

The MDR is a 'a into memory.

The Memory Data Register is half of a minimal interface between a microprogram and computer storage, the other half is a memory address register.

Far more complex memory interfaces exist, but this is the simplest that can work.

    The Memory Data Register (MDR) contains the data value being fetched or stored. We might be tempted to say that the MDR should be W bits wide, where W is the cell size. However on most computers the cell size is only 8-bits, and most data values occupy multiple cells. Thus the size of the MDR is usually a multiple of 8. Typical values of MDR width are 32 and 64 bits, which would allow us to fetch, in a single step, either an integer or a real value.

    For example, to retrieve the contents of cell 123, we would load the value 123 (in binary, of course) into the MAR and perform a fetch operation. When the operation is done, a copy of the contents of cell 123 would be in the MDR. To store the value 98 into cell 4, we load a 4 into the MAR and a 98 into the MDR and perform a store. When the operation is completed the contents of cell 4 will have been set to 98, discarding whatever was there previously.

This computer hardware article is a stub. You can help Wikipedia by expanding it.v · Categories: Digital registers Computer hardware stubs Wikimedia Foundation. 2010. Игры ⚽ Поможем сделать НИР Memory address register Microassembler Look at other dictionaries: Memory Data Register — MDR Das memory data register (MDR) ist ein Register der CPU und enthält die Daten, die in das RAM gespeichert oder aus dem RAM gelesen werden sollen. Es verhält sich daher wie ein Puffer, der die Daten bereithält, bis sie per Steuersignal in das… …   Deutsch Wikipedia Memory address register — The Memory Address Register (MAR) is a CPU register that either stores the memory address from which data will be fetched to the CPU or the address to which data will be sent and stored. In other words, MAR holds the memory location of data that… …   Wikipedia Memory buffer register — A Memory Buffer Register (MBR) is the register in a computer s processor, or central processing unit, CPU, that stores the data being transferred to and from the immediate access store. It acts as a buffer allowing the processor and memory units… …   Wikipedia Register allocation — In compiler optimization, register allocation is the process of multiplexing a large number of target program variables onto a small number of CPU registers. The goal is to keep as many operands as possible in registers to maximise the execution… …   Wikipedia memory abnormality — Introduction       any of the disorders that affect the ability to remember.       Disorders of memory must have been known to the ancients and are mentioned in several early medical texts, but it was not until the closing decades of the 19th… …   Universalium Data General Nova — System Data General Nova 1200 front panel …   Wikipedia Processor register — In computer architecture, a processor register is a small amount of storage available as part of a CPU or other digital processor. Such registers are (typically) addressed by mechanisms other than main memory and can be accessed more quickly.… …   Wikipedia Memory disambiguation — is a set of techniques employed by high performance out of order execution microprocessors that execute memory access instructions (loads and stores) out of program order. The mechanisms for performing memory disambiguation, implemented using… …   Wikipedia Memory architecture — describes the methods used to implement electronic computer data storage in a manner that is a combination of the fastest, most reliable, most durable, and least expensive way to store and retrieve information. Depending on the specific… …   Wikipedia Data (Star Trek) — Data Data on the bridge of the Enterprise D Species Android Home planet Omicron Theta Affiliation United Federation of Planets Starfleet …   Wikipedia 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”