
:''RAM redirects here. For other meanings of the word ram see Ram (disambiguation).'' Random Access Memory or RAM is a type of computer storage whose contents can be accessed in any order. This is in contrast to ''sequential memory devices'' such as magnetic tapes, discs and drums, in which the mechanical movement of the storage medium forces the computer to access data in a fixed order. It is usually implied that RAM can be both written to and read from, in contrast to Read-Only Memory or Read-only memory. RAM is usually used for primary storage in computers to hold actively-used and actively-changing information, although some devices use certain types of RAM to provide long term secondary storage. ==Overview== Computers use RAM to hold the program code and data during execution. One defining characteristic of RAM is that its accesses to different memory locations are almost always completed at about the same speed, in contrast to some other technologies that required a certain delay time for a bit or byte to “come around”. Early vacuum tube-based systems behaved much like modern RAM, even though the devices failed much more frequently. Core memory, which used wires attached to small ferrite electromagnetism cores, also had roughly equal access time (the term “core” is still used by some programmers to describe the RAM at the heart of a computer). The basic ideas behind tube and core memory are still used in modern RAM implemented with integrated circuits. Alternative primary storage mechanisms usually involved a non-uniform delay for memory access. Delay line memory used a sequence of sound wave pulses in mercury (element)-filled tubes to hold a series of bits. Drum memory acted much like the modern hard disk, storing data magnetism in continuous circular bands. (See primary storage for a greater discussion of these alternatives and others.) Many types of RAM are ''volatile'', which means that unlike some other forms of computer storage such as disk storage and tape storage, they lose their data when the computer is powered down. Modern RAM generally stores a bit of data as either a charge in a capacitor, as in dynamic RAM, or the state of a flip-flop, as in static RAM. Currently, there are several types of NVRAM under development, which will preserve data while powered down. Technologies that are being used include Carbon_nanotube and Magnetic_tunnel_effect. In the summer of 2003, a 128 Kibibit MRAM chip was introduced, which was manufactured with 0.18 micrometre technology. The core technology of MRAM is based on the magnetic tunnel effect. In June of 2004, Infineon unveiled a 16-Mebibit prototype based on 0.18 µm technology once again. In 2005, [http://www.compu-technics.com Compu-Technics Inc.] presented a 256 GiB/4GHz non-volatile Magnetic RAM array, as well as a notebook using this chip, SG220. As for carbon nanotube memory, a high-tech startup [http://www.nantero.com/ Nantero] has built a functioning prototype 10 GiB array in 2004. An interesting use of RAM is allocating parts of it as a partition, effectively acting as a hard drive, only much faster. It is usually referred to as a ramdisk. == Common types of RAM == *SRAM or Static Random Access Memory *NV-RAM or NRAM *DRAM or Dynamic Random Access Memory **Fast Page Mode DRAM **EDO RAM or Extended Data Out DRAM **XDR DRAM **SDRAM or Synchronous DRAM ***DDR SDRAM or Double Data Rate Synchronous DRAM ***RDRAM or Rambus DRAM == Uncommon types of RAM == * Dual-ported RAM * Video RAM, a dual-port memory with one random access port and one sequential access port. This is becoming more popular as people need more and more video memory. See description under Dynamic random access memory. * WRAM * MRAM * FeRAM == RAM packaging == Semiconductor RAM is produced as integrated circuits (ICs). RAM ICs are often assembled into plug-in modules. Some standard module types are: * Single in-line Pin Package (Single in-line package) * Dual in-line Package (Dual in-line package) * Single in-line memory module (SIMM) * Dual in-line memory module (DIMM) * Rambus modules are actually DIMMs, but are often referred to (by Rambus themselves and others) as RDRAM due to their proprietary slot. * Small outline DIMM (SO-DIMM). Smaller version of the DIMM, used in laptops. Comes in versions with 72 (32 bit), 144 (64 bit), 200 (72 bit) pins * Small outline RIMM (SO-RIMM) == Buffering of RAM modules == Larger RAM modules have significantly higher capacity loads for their signal lines. Buffering reduces these loads, but increases latency. * Unregistered RAM * Registered RAM: Address and control lines are buffered, data lines are unbuffered * Fully buffered RAM: All the lines are buffered ==Memory wall== In today's computers memory access is becoming very slow when compared to Central processing unit cycles since most computers use cheap, but comparatively slow, DRAM for the main memory. Hence, the memory access, like hard disk access, might become the term that bounds computation speed. This is another important bound on fast computations. ==Shadow RAM== Shadow RAM is the part of RAM with its contents copied from ROMs from where it will run much faster [http://hardwarehell.com/articles/shadowram.htm]. ROMs are slower to use than RAMs. The original ROM is disabled and the new location on the RAM is write protected. This process is also called shadowing. ==External links== * [http://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci214255,00.html Definition] * [http://webopedia.com/TERM/R/RAM.html What is RAM?] * Article "[http://www.howstuffworks.com/ram.htm How RAM Works]" by Jeff Tyson and Dave Coustan * [http://mxt.sourceforge.net/ Memory eXpansion Technology] * [http://www.corsairmemory.com/memory_basics/153707/index.html Corsair Memory Basics Presentation] (flash required) Digital electronics Computer memory th:แรม
==Matched pair== What about some info on what a "matched pair" is? --Anonymous :There is a short note on this in the DDR SDRAM article, but it could do with more detail. One contributor remembers them being used in old Macs, too. If you find out anything, please help us by adding it to Wikipedia. -- User:Heron 17:59, 20 Aug 2004 (UTC) ==MicroDIMM?== any information about this form factor? --Anonymous ==Questions concerning memory== When you refer to the layout of the pc memmory, do you mean tha internal memory(RAM) or all memory together(ROM)? Has logical adressing in real mode something to do with virtual addressing? Or are these types two different things? --Anonymous ==Article naming== How about moving Random Access Memory to Random access memory since the only reason it's capitalised is because it's mostly used as an acronym? User:Quoth 00:38, 11 Apr 2005 (UTC) :Oops, should've been watching the article. WKP policy is actually not to use the capitalized form of a term such as RAM; please see the Wikipedia:Naming conventions (capitalization). I guess I should just go ahead and re-rename the article, but I'll wait a day or two to let it sink in. -User:Wernher 03:24, 19 Jun 2005 (UTC) ==Simple English== Can anyone provide a Simple English page for RAM? User:Cuahl 16:51, 12 Jun 2005 (UTC)
#redirect Talk:Random Access Memory
#redirect Random Access Memory
See other meanings of words starting from letter:
Words begining with Random_Access_Memory:
Random-access_memory
Random_Access_Memory
Random_Access_Memory
Random_access_memory
Random_access_memory
Random Access Memory
:''RAM redirects here. For other meanings of the word ram see Ram (disambiguation).'' Random Access Memory or RAM is a type of computer storage whose contents can be accessed in any order. This is in contrast to ''sequential memory devices'' such as magnetic tapes, discs and drums, in which the mechanical movement of the storage medium forces the computer to access data in a fixed order. It is usually implied that RAM can be both written to and read from, in contrast to Read-Only Memory or Read-only memory. RAM is usually used for primary storage in computers to hold actively-used and actively-changing information, although some devices use certain types of RAM to provide long term secondary storage. ==Overview== Computers use RAM to hold the program code and data during execution. One defining characteristic of RAM is that its accesses to different memory locations are almost always completed at about the same speed, in contrast to some other technologies that required a certain delay time for a bit or byte to “come around”. Early vacuum tube-based systems behaved much like modern RAM, even though the devices failed much more frequently. Core memory, which used wires attached to small ferrite electromagnetism cores, also had roughly equal access time (the term “core” is still used by some programmers to describe the RAM at the heart of a computer). The basic ideas behind tube and core memory are still used in modern RAM implemented with integrated circuits. Alternative primary storage mechanisms usually involved a non-uniform delay for memory access. Delay line memory used a sequence of sound wave pulses in mercury (element)-filled tubes to hold a series of bits. Drum memory acted much like the modern hard disk, storing data magnetism in continuous circular bands. (See primary storage for a greater discussion of these alternatives and others.) Many types of RAM are ''volatile'', which means that unlike some other forms of computer storage such as disk storage and tape storage, they lose their data when the computer is powered down. Modern RAM generally stores a bit of data as either a charge in a capacitor, as in dynamic RAM, or the state of a flip-flop, as in static RAM. Currently, there are several types of NVRAM under development, which will preserve data while powered down. Technologies that are being used include Carbon_nanotube and Magnetic_tunnel_effect. In the summer of 2003, a 128 Kibibit MRAM chip was introduced, which was manufactured with 0.18 micrometre technology. The core technology of MRAM is based on the magnetic tunnel effect. In June of 2004, Infineon unveiled a 16-Mebibit prototype based on 0.18 µm technology once again. In 2005, [http://www.compu-technics.com Compu-Technics Inc.] presented a 256 GiB/4GHz non-volatile Magnetic RAM array, as well as a notebook using this chip, SG220. As for carbon nanotube memory, a high-tech startup [http://www.nantero.com/ Nantero] has built a functioning prototype 10 GiB array in 2004. An interesting use of RAM is allocating parts of it as a partition, effectively acting as a hard drive, only much faster. It is usually referred to as a ramdisk. == Common types of RAM == *SRAM or Static Random Access Memory *NV-RAM or NRAM *DRAM or Dynamic Random Access Memory **Fast Page Mode DRAM **EDO RAM or Extended Data Out DRAM **XDR DRAM **SDRAM or Synchronous DRAM ***DDR SDRAM or Double Data Rate Synchronous DRAM ***RDRAM or Rambus DRAM == Uncommon types of RAM == * Dual-ported RAM * Video RAM, a dual-port memory with one random access port and one sequential access port. This is becoming more popular as people need more and more video memory. See description under Dynamic random access memory. * WRAM * MRAM * FeRAM == RAM packaging == Semiconductor RAM is produced as integrated circuits (ICs). RAM ICs are often assembled into plug-in modules. Some standard module types are: * Single in-line Pin Package (Single in-line package) * Dual in-line Package (Dual in-line package) * Single in-line memory module (SIMM) * Dual in-line memory module (DIMM) * Rambus modules are actually DIMMs, but are often referred to (by Rambus themselves and others) as RDRAM due to their proprietary slot. * Small outline DIMM (SO-DIMM). Smaller version of the DIMM, used in laptops. Comes in versions with 72 (32 bit), 144 (64 bit), 200 (72 bit) pins * Small outline RIMM (SO-RIMM) == Buffering of RAM modules == Larger RAM modules have significantly higher capacity loads for their signal lines. Buffering reduces these loads, but increases latency. * Unregistered RAM * Registered RAM: Address and control lines are buffered, data lines are unbuffered * Fully buffered RAM: All the lines are buffered ==Memory wall== In today's computers memory access is becoming very slow when compared to Central processing unit cycles since most computers use cheap, but comparatively slow, DRAM for the main memory. Hence, the memory access, like hard disk access, might become the term that bounds computation speed. This is another important bound on fast computations. ==Shadow RAM== Shadow RAM is the part of RAM with its contents copied from ROMs from where it will run much faster [http://hardwarehell.com/articles/shadowram.htm]. ROMs are slower to use than RAMs. The original ROM is disabled and the new location on the RAM is write protected. This process is also called shadowing. ==External links== * [http://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci214255,00.html Definition] * [http://webopedia.com/TERM/R/RAM.html What is RAM?] * Article "[http://www.howstuffworks.com/ram.htm How RAM Works]" by Jeff Tyson and Dave Coustan * [http://mxt.sourceforge.net/ Memory eXpansion Technology] * [http://www.corsairmemory.com/memory_basics/153707/index.html Corsair Memory Basics Presentation] (flash required) Digital electronics Computer memory th:แรม
Random Access Memory
==Matched pair== What about some info on what a "matched pair" is? --Anonymous :There is a short note on this in the DDR SDRAM article, but it could do with more detail. One contributor remembers them being used in old Macs, too. If you find out anything, please help us by adding it to Wikipedia. -- User:Heron 17:59, 20 Aug 2004 (UTC) ==MicroDIMM?== any information about this form factor? --Anonymous ==Questions concerning memory== When you refer to the layout of the pc memmory, do you mean tha internal memory(RAM) or all memory together(ROM)? Has logical adressing in real mode something to do with virtual addressing? Or are these types two different things? --Anonymous ==Article naming== How about moving Random Access Memory to Random access memory since the only reason it's capitalised is because it's mostly used as an acronym? User:Quoth 00:38, 11 Apr 2005 (UTC) :Oops, should've been watching the article. WKP policy is actually not to use the capitalized form of a term such as RAM; please see the Wikipedia:Naming conventions (capitalization). I guess I should just go ahead and re-rename the article, but I'll wait a day or two to let it sink in. -User:Wernher 03:24, 19 Jun 2005 (UTC) ==Simple English== Can anyone provide a Simple English page for RAM? User:Cuahl 16:51, 12 Jun 2005 (UTC)
Random access memory
#redirect Talk:Random Access Memory
Random access memory
#redirect Random Access Memory
See other meanings of words starting from letter:
R
RA | RB | RC | RD | RE | RF | RG | RH | RI | RJ | RK | RL | RM | RN | RO | RP | RS | RT | RU | RW | RX | RY | RZ |Words begining with Random_Access_Memory:
Random-access_memory
Random_Access_Memory
Random_Access_Memory
Random_access_memory
Random_access_memory
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