JEDEC memory standards

The Joint Electron Device Engineering Council characterizes its standardization efforts as follows:

{{cite web

|author=JEDEC Solid State Technology Association

|title=Terms, Definitions, and Letter Symbols for Microcomputers, Microprocessors, and Memory Integrated Circuits

|work=JESD 100B.01

|date=December 2002

|page=8

|url=http://www.jedec.org/download/search/JESD100B01.pdf

|access-date=2009-04-05

}} {{quote|JEDEC standards and publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for use by those other than JEDEC members, whether the standard is to be used either domestically or internationally.}}

The December 2002 JEDEC Standard 100B.01 is entitled Terms, Definitions, and Letter Symbols for Microcomputers, Microprocessors, and Memory Integrated Circuits. The purpose of the standard is to promote the uniform use of symbols, abbreviations, terms, and definitions throughout the semiconductor industry.

The specification defines the two common units of information:Ref. ANSI X3.172.

• The bit (b) is the smallest unit of information in the binary numeration system and is represented by the digits 0 and 1.
• The byte (B) is a binary character string typically operated upon as one unit. It is usually shorter than a computer word.

The specification contains citations of the commonly used prefixes kilo, mega, and giga to prefix units of semiconductor storage capacity.

The specification cites three prefixes as follows, with the note that these prefixes are included in the document only to reflect common usage.

• kilo (K) (as a prefix to units of semiconductor storage capacity): A multiplier equal to 1024 (2¹⁰).{{cite web|url=http://www.jedec.org/standards-documents/dictionary/terms/kilo-k-prefix-units-semiconductor-storage-capacity|title=JEDEC dictionary entry: kilo (K) (as a prefix to units of semiconductor storage capacity)}}
• mega (M) (as a prefix to units of semiconductor storage capacity): A multiplier equal to {{val|1048576}} (2²⁰ or K², where K = 1024).{{cite web|url=http://www.jedec.org/standards-documents/dictionary/terms/mega-m-prefix-units-semiconductor-storage-capacity|title=JEDEC dictionary entry: mega (M) (as a prefix to units of semiconductor storage capacity)}}
• giga (G) (as a prefix to units of semiconductor storage capacity): A multiplier equal to {{val|1073741824}} (2³⁰ or K³, where K = 1024).{{cite web|url=https://www.jedec.org/standards-documents/dictionary/terms/giga-g-prefix-units-semiconductor-storage-capacity|title=JEDEC dictionary entry: giga (G) (as a prefix to units of semiconductor storage capacity)}}

It refers to the IEEE/ASTM SI 10-1997 standard as stating that "this practice frequently leads to confusion and is deprecated". The document further refers to the description of the IEC binary prefixes in Amendment 2 of IEC 60027-2, "Letter symbols to be used in electrical technology", for an alternate system of prefixesQuote from JEDEC Standard 100B.01, page 8:{{quote|The definitions of kilo, giga, and mega based on powers of two are included only to reflect common usage. IEEE/ASTM SI 10-1997 states "This practice frequently leads to confusion and is deprecated." Further confusion results from the popular use of the megabyte representing 1 024 000 bytes to define the capacity of the 1.44-MB high-density diskette. An alternative system is found in Amendment 2 to IEC 60027-2: Letter symbols to be used in electrical technology – Part 2.}} and includes a table of the IEC prefixes in the note.

The document notes that these prefixes are used in their decimal sense for serial communication data rates measured in bits.

The JEDEC terms dictionary further includes, under the entry for mega, definitions for the binary prefixes kibi (Ki), mebi (Mi), gibi (Gi), and tebi (Ti) as powers of 2, and kilo, mega, giga, and tera as powers of 10.[http://www.jedec.org/standards-documents/dictionary/terms/mega-m-prefix-units-semiconductor-storage-capacity JEDEC dictionary entry] For example,

: 2⁴⁰ tebi Ti tera + binary: (2¹⁰)⁴ = {{val|1099511627776}} tera: (10³)⁴

The JEDEC DDR3 SDRAM standard JESD-79-3f uses Mb and Gb to specify binary memory capacity:{{cite web|url=http://www.jedec.org/standards-documents/docs/jesd-79-3d|title = DDR3 SDRAM STANDARD | JESD79-3F|publisher=JEDEC|date=Jul 2012|access-date=2022-08-21}} "The purpose of this Standard is to define the minimum set of requirements for JEDEC compliant 512 Mb through 8 Gb for x4, x8, and x16 DDR3 SDRAM devices."

The standard JESD21-C: Configurations for Solid State Memories is maintained by JEDEC committee JC41. This committee consists of members from manufacturers of microprocessors, memory ICs, memory modules, and other components, as well as component integrators, such as video card and personal computer makers. Standard 21 is published in loose-leaf binder format to accommodate frequent updates.

The documentation of modern memory modules, such as the standards for the memory ICs

{{citation

|author=JEDEC

|title=Double Data Rate (DDR) SDRAM Specification

|url=http://www.jedec.org/download/search/JESD79E.pdf |url-status=dead

|archive-url=https://web.archive.org/web/20061002004407/http://www.jedec.org/download/search/JESD79E.pdf

|archive-date=2006-10-02 |access-date=2013-08-08

}} and a reference design of the module

{{citation

|author=JEDEC

|title=EP2-2100 DDR2 SDRAM 32b-SO-DIMM Reference Design Specification

|year=2007

|url=http://www.jedec.org/download/search/4_20_16R16.pdf

|access-date=2009-04-05

}} requires over one hundred pages. The standards specify the physical and electrical characteristics of the modules, and include the data for computer simulations of the memory module operating in a system.

{{citation

|author=JEDEC

|title=Bit Wide TTL SRAM

|url=http://www.jedec.org/download/search/3_07_01R5.pdf |url-status=dead

|archive-url=https://web.archive.org/web/20030420100639/http://www.jedec.org/download/search/3_07_01R5.pdf

|archive-date=2003-04-20 |access-date=2013-08-08

}}

Memory modules of the DDR2-SDRAM type are available for laptop, desktop, and server computers in a wide selection of capacities and access speeds. The standards specify memory module label formats for end-user markets.

{{citation

|author=JEDEC

|title=Preliminary publication of JEDEC Semiconductor Memory Standard

|url=http://www.jedec.org/download/search/N06-NM5.pdf |url-status=dead

|archive-url=https://web.archive.org/web/20070926225548/http://www.jedec.org/download/search/N06-NM5.pdf

|archive-date=2007-09-26 |access-date=2013-08-08

}} For example:

{{quote|1=1GB 2Rx4 PC2-3200P-333-11-D2 is a 1 GB DDR2 Registered DIMM, with address/command parity function, using 2 ranks of x4 SDRAMs operational to PC2-3200 performance with CAS Latency = 3, tRCD = 3, tRP = 3, using JEDEC SPD revision 1.1, raw card reference design file D revision 2 used for the assembly.}}

• IEC 60027
• ISO/IEC 80000
• Timeline of binary prefixes

{{reflist|group=note}}

{{reflist|30em}}

• [http://www.jedec.org/standards-documents Online JEDEC documents]
• [http://www.jedec.org/sites/default/files/docs/JESD218.pdf JESD218]

Category:Units of information

Category:JEDEC standards