Main memory - Revision history

Jnc: +See also

2019-09-11T15:10:26Z

+See also

Jnc: this too

2018-12-15T14:32:58Z

this too

Jnc: +cat

2018-12-15T14:31:36Z

+cat

Jnc: add harvard/vonN, links

2018-10-06T23:12:26Z

add harvard/vonN, links

Jnc: avoid redir

2017-09-21T19:43:45Z

avoid redir

Jnc: A decent start

2016-11-12T02:57:15Z

A decent start

New page

'''Main memory''' refers to the memory from which the [[CPU]] reads its instructions as it executes them; typically, a simple CPU will read an instruction from main memory, execute it, and then read the next instruction, repeating the process indefinitely.

(With the advent of modern CPUs, which for purposes of increased speed usually have multiple instructions in execution in parallel, the simple model above no longer actually applies.)

Main memory is also used to store data for immediate access by the CPU.
Modern computers usually have a [[cache]], in which the machine keeps both instructions and data which are in current use. However, the operation of the cache is usually invisible to the program/programmer; to them, all the instructions and data appear to be stored in main memory.

A number of different technologies have been used over time for main memory. The very earliest computers used technology such as acoustic delay lines and storage cathode ray tubes; in some low-cost computers, magnetic drums were used. These were all replaced by the far superior (compared to its predecessors) [[core memory]]. Eventually, it was replaced by semi-conductor memory, principally [[dynamic RAM]].

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 The very earliest computers used technology such as acoustic [[delay line]]s and storage [[cathode ray tube]]s; in some low-cost computers, [[magnetic storage|magnetic]] [[drum]]s were used. These were all replaced by the far superior (compared to its predecessors) [[core memory]]. Eventually, it in turn was replaced by [[semiconductor]] memory, principally [[dynamic RAM]].
 [[Category: CPU Basics]]
 [[Category: Memory Basics]]

← Older revision		Revision as of 14:32, 15 December 2018
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	[[Category: CPU Basics]]		[[Category: CPU Basics]]
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← Older revision		Revision as of 14:31, 15 December 2018
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	The very earliest computers used technology such as acoustic [[delay line]]s and storage [[cathode ray tube]]s; in some low-cost computers, [[magnetic storage\|magnetic]] [[drum]]s were used. These were all replaced by the far superior (compared to its predecessors) [[core memory]]. Eventually, it in turn was replaced by [[semiconductor]] memory, principally [[dynamic RAM]].		The very earliest computers used technology such as acoustic [[delay line]]s and storage [[cathode ray tube]]s; in some low-cost computers, [[magnetic storage\|magnetic]] [[drum]]s were used. These were all replaced by the far superior (compared to its predecessors) [[core memory]]. Eventually, it in turn was replaced by [[semiconductor]] memory, principally [[dynamic RAM]].
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		+	[[Category: CPU Basics]]

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-'''Main memory''' refers to the memory from which the [[Central Processing Unit|CPU]] reads its instructions as it executes them; typically, a simple CPU will read an instruction from main memory, execute it, and then read the next instruction, repeating the process indefinitely.
+'''Main memory''' refers to the [[memory]] from which the [[Central Processing Unit|CPU]] reads its [[instruction]]s as it [[execute]]s them; typically, a simple CPU will read an instruction from main memory, execute it, and then read the next instruction, repeating the process indefinitely.
 (With the advent of modern CPUs, which for purposes of increased speed usually have multiple instructions in execution in parallel, the simple model above no longer actually applies.)
-Main memory is also used to store data for immediate access by the CPU.
+Main memory is also used to store data for immediate access by the CPU. Computers which keep instructions and data in the same memory are called 'von Neumann' [[architecture]]s; those which keep instructions and memory in separate memories, usually reached via separate [[bus]]ses, are called 'Harvard' architectures.
-Modern computers usually have a [[cache]], in which the machine keeps both instructions and data which are in current use. However, the operation of the cache is usually invisible to the program/programmer; to them, all the instructions and data appear to be stored in main memory.
+Modern computers usually have a [[cache]], in which the machine keeps both instructions and data which are in current use. However, the operation of the cache is usually invisible to the [[program]]/[[programmer]]; to them, all the instructions and data appear to be stored in main memory.
-A number of different technologies have been used over time for main memory. The very earliest computers used technology such as acoustic delay lines and storage cathode ray tubes; in some low-cost computers, magnetic drums were used. These were all replaced by the far superior (compared to its predecessors) [[core memory]]. Eventually, it was replaced by semi-conductor memory, principally [[dynamic RAM]].
+A number of different technologies have been used over time for main memory.