The JEDEC memory standards are the specifications for semiconductor memory circuits and similar storage devices promulgated by the JEDEC Solid State Technology Association, a semiconductor trade and engineering standardization organization.

JEDEC Standard 100B.01 specifies common terms, units, and other definitions in use in the semiconductor industry. JESC21-C specifies semiconductor memories from the 256 bit static RAM to the latest DDR3 SDRAM modules.

JEDEC standardization goals

JEDEC characterizes its standardization efforts as follows:^[1]

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.

JEDEC Standard 100B.01

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.^[1]

Units of information storage

The specification defines the two common units of information storage:

• bit (b): In the binary numeration system, either of the digits 0 or 1. (Ref. ANSI X3.172.)
• byte (B): A binary character string operated upon as a unit and usually shorter than a computer word. (Ref. ANSI X3.172.) NOTE: A byte is usually eight bits.

Unit prefixes for semiconductor storage capacity

The specification contains definitions of the commonly used prefixes kilo, mega, and giga, usually combined with the units byte and bit to designate multiples of the units.

The specification defines these prefixes as follows:

• kilo (K): A multiplier equal to 1024 (2¹⁰).
• mega (M): A multiplier equal to 1048576 (2²⁰ or K², where K = 1024).
• giga (G): A multiplier equal to 1073741824 (2³⁰ or K³, where K = 1024).

The specification notes that these prefixes are included in the document only to reflect common usage. 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 the reader 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 prefixes^{[notes 1]} and includes a table of the IEC prefixes in the JEDEC specification.

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

All JEDEC standards avoid the use of the terms megabit, megabyte, gigabyte, terabyte, etc, and refer to memory capacity as a number followed by the units. (64Mb, 256MB, 1GB, or 4TB.)^{[citation needed]}

JESD21-C

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. Additions to Standard 21 are so frequent that it is published in loose-leaf format and comes in a three-ring binder.

In the 1980s the configuration of a family of memories could be specified on a single page. Modern memory modules require over 100 pages; standards for the memory IC^[2] and a reference design of the module.^[3] The standards specify the physical dimensions for the module, the electrical characteristics for the module and even the data for doing computer simulations of the memory module operating in a system.^[4]

A memory module like the DDR2-SDRAM is available for laptop, desktop, and server computers. There is also a wide selection of memory capacities and speeds. The standards specify memory module label formats for "End User Markets".^[5] For example:

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.

Notes

References

External links

• Online JEDEC documents