EDRAM
Encyclopedia
eDRAM stands for "embedded
DRAM
", a capacitor
-based dynamic random access memory
integrated on the same die
as an ASIC
or processor
. The cost-per-bit is higher than for stand-alone DRAM chips but in many applications the performance advantages of placing the eDRAM on the same chip as the processor outweighs the cost disadvantage compared with external memory.
Embedding memory on the ASIC or processor allows for much wider bus
ses and higher operation speeds, and due to much higher density of DRAM in comparison to SRAM
, larger amounts of memory can be installed on smaller chips if eDRAM is used instead of eSRAM. eDRAM requires additional fab process steps compared with embedded SRAM, which raises cost, but the 3X area savings of eDRAM memory offsets the process cost when a significant amount of memory is used in the design.
eDRAM memories, like all DRAM memories, require periodic refreshing of the memory cells, which adds complexity. However if the memory refresh controller is embedded along with the eDRAM memory, the remainder of the ASIC can treat the memory like a simple SRAM type such as in 1T-SRAM
.
eDRAM is used in IBM's POWER7
processor and in many game consoles and other devices, including Sony
's PlayStation 2
, Sony's PlayStation Portable
, Nintendo
's GameCube, Nintendo's Wii
, Apple Inc.'s iPhone
, Microsoft
's Zune HD
, and Microsoft's Xbox 360
.
Embedded system
An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...
DRAM
Dynamic random access memory
Dynamic random-access memory is a type of random-access memory that stores each bit of data in a separate capacitor within an integrated circuit. The capacitor can be either charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1...
", a capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
-based dynamic random access memory
Dynamic random access memory
Dynamic random-access memory is a type of random-access memory that stores each bit of data in a separate capacitor within an integrated circuit. The capacitor can be either charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1...
integrated on the same die
Die (integrated circuit)
A die in the context of integrated circuits is a small block of semiconducting material, on which a given functional circuit is fabricated.Typically, integrated circuits are produced in large batches on a single wafer of electronic-grade silicon or other semiconductor through processes such as...
as an ASIC
Application-specific integrated circuit
An application-specific integrated circuit is an integrated circuit customized for a particular use, rather than intended for general-purpose use. For example, a chip designed solely to run a cell phone is an ASIC...
or processor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
. The cost-per-bit is higher than for stand-alone DRAM chips but in many applications the performance advantages of placing the eDRAM on the same chip as the processor outweighs the cost disadvantage compared with external memory.
Embedding memory on the ASIC or processor allows for much wider bus
Computer bus
In computer architecture, a bus is a subsystem that transfers data between components inside a computer, or between computers.Early computer buses were literally parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same...
ses and higher operation speeds, and due to much higher density of DRAM in comparison to SRAM
Static random access memory
Static random-access memory is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM , it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit...
, larger amounts of memory can be installed on smaller chips if eDRAM is used instead of eSRAM. eDRAM requires additional fab process steps compared with embedded SRAM, which raises cost, but the 3X area savings of eDRAM memory offsets the process cost when a significant amount of memory is used in the design.
eDRAM memories, like all DRAM memories, require periodic refreshing of the memory cells, which adds complexity. However if the memory refresh controller is embedded along with the eDRAM memory, the remainder of the ASIC can treat the memory like a simple SRAM type such as in 1T-SRAM
1T-SRAM
1T-SRAM is a pseudostatic random-access memory technology introduced by MoSys, Inc., which offers a high-density alternative to traditional static random access memory in embedded memory applications...
.
eDRAM is used in IBM's POWER7
POWER7
POWER7 is a Power Architecture microprocessor released in 2010 that succeeded the POWER6. POWER7 was developed by IBM at several sites including IBM's Rochester, MN; Austin, TX; Essex Junction, Vermont; T. J. Watson Research Center, NY; Bromont, QC and Böblingen, Germany laboratories...
processor and in many game consoles and other devices, including Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
's PlayStation 2
PlayStation 2
The PlayStation 2 is a sixth-generation video game console manufactured by Sony as part of the PlayStation series. Its development was announced in March 1999 and it was first released on March 4, 2000, in Japan...
, Sony's PlayStation Portable
PlayStation Portable
The is a handheld game console manufactured and marketed by Sony Corporation Development of the console was announced during E3 2003, and it was unveiled on , 2004, at a Sony press conference before E3 2004...
, Nintendo
Nintendo
is a multinational corporation located in Kyoto, Japan. Founded on September 23, 1889 by Fusajiro Yamauchi, it produced handmade hanafuda cards. By 1963, the company had tried several small niche businesses, such as a cab company and a love hotel....
's GameCube, Nintendo's Wii
Wii
The Wii is a home video game console released by Nintendo on November 19, 2006. As a seventh-generation console, the Wii primarily competes with Microsoft's Xbox 360 and Sony's PlayStation 3. Nintendo states that its console targets a broader demographic than that of the two others...
, Apple Inc.'s iPhone
IPhone
The iPhone is a line of Internet and multimedia-enabled smartphones marketed by Apple Inc. The first iPhone was unveiled by Steve Jobs, then CEO of Apple, on January 9, 2007, and released on June 29, 2007...
, Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
's Zune HD
Zune HD
The Zune HD is a portable media player in the Zune product family released on September 15, 2009 by Microsoft. It is a direct competitor with the Apple iPod and iPhone series of mobile devices. It was initially released in 16 and 32 GB capacities. A 64 GB version was released on April 9, 2010...
, and Microsoft's Xbox 360
Xbox 360
The Xbox 360 is the second video game console produced by Microsoft and the successor to the Xbox. The Xbox 360 competes with Sony's PlayStation 3 and Nintendo's Wii as part of the seventh generation of video game consoles...
.
External links
- http://www.cs.unc.edu/~jp/DRAM.pdf
- Day dawns for eDRAM
- http://www.necelam.com/edram90/
- http://www.findarticles.com/p/articles/mi_qa3751/is_200501/ai_n9521086
- http://arstechnica.com/news.ars/post/20070214-8842.html
- http://www.allbusiness.com/electronics/computer-electronics-manufacturing/6302349-1.html