Non-volatile random-access memory: Difference between revisions

Revision as of 05:42, 8 May 2021

Revision as of 17:47, 19 May 2021

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{{short description|Type of computer memory}}

{{See also|Nonvolatile BIOS memory}}

{{Memory types}}

{{short description|Type of computer memory}}

'''Non-volatile random-access memory''' ('''NVRAM''') is [[random-access memory]] that retains data without applied power. This is in contrast to [[dynamic random-access memory]] (DRAM) and [[static random-access memory]] (SRAM), which both maintain data only for as long as power is applied, or such forms of memory as [[magnetic tape]], which cannot be randomly accessed but which retains data indefinitely without electric power.

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If the main memory of a computer system were non-volatile, it would greatly reduce the time required to start a system after a power interruption. Current existing types of semiconductor non-volatile memory have limitations in memory size, power consumption, or operating life that make them impractical for main memory. Development is going on for the use of non-volatile memory chips as a system's main memory, as [[persistent memory]]. Known as [[NVDIMM#Types|NVDIMM-P]], which standard has been published in 2021.<ref>{{cite press release|url=https://www.jedec.org/news/pressreleases/jedec-ddr5-nvdimm-p-standards-under-development|title=JEDEC DDR5 & NVDIMM-P Standards Under Development|date=2017-03-30|publisher=[[JEDEC]]}}</ref><ref>{{cite press release|url=https://www.jedec.org/news/pressreleases/jedec-hold-workshops-ddr5-lpddr5-nvdimm-p-standards|title=JEDEC to Hold Workshops for DDR5, LPDDR5 & NVDIMM-P Standards|date=2019-09-05|publisher=JEDEC}}</ref><ref>{{cite press release|url=https://www.jedec.org/news/pressreleases/jedec-publishes-ddr4-nvdimm-p-bus-protocol-standard|title=JEDEC Publishes DDR4 NVDIMM-P Bus Protocol Standard|date=2021-02-17|publisher=JEDEC}}</ref>

==Early NVRAMs==

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===Millipede memory===

{{Main|Millipede memory}}

Perhaps one of the more innovative solutions is [[IBM Millipede|millipede memory]], developed by [[IBM]]. Millipede is, in essence, a [[punched card]] rendered using [[nanotechnology]] in order to dramatically increase areal density. Although it was planned to introduce Millipede as early as 2003, unexpected problems in development delayed this until 2005, by which point it was no longer competitive with flash. In theory the technology offers storage densities on the order of 1 Tbit/in² (≈394 Gbit/cm²²), greater than even the best [[hard drive]] technologies currently in use ([[perpendicular recording]] offers 636 Gbit/in² (≈250.4 Gbit/cm²²) as of Dec. 2011<ref name=636-gigabits>{{cite press release | url = http://www.hitachigst.com/press-room/2011/hitachi-gst-ships-one-terabyte-per-platter-hard-drives | title = Hitachi GST Ships One Terabyte Per Platter Hard Drives | access-date = 2011-12-17 | date = 2011-08-03 | publisher = [[Hitachi Global Storage Technologies]] | url-status = dead | archive-url = https://web.archive.org/web/20111026210519/http://www.hitachigst.com/press-room/2011/hitachi-gst-ships-one-terabyte-per-platter-hard-drives | archive-date = 2011-10-26}}</ref>), but future [[heat-assisted magnetic recording]] and [[patterned media]] together could support densities of 10 Tbit/in²<ref name=10-terabits>{{cite web | url = https://arstechnica.com/science/news/2010/05/new-hard-drive-write-method-packs-in-one-terabyte-per-inch.ars | title = New hard drive write method packs in one terabit per inch | access-date = 2011-12-17 | last = Johnston | first = Casey | date = 2011-05-07 | website = Ars Technica}}</ref> (≈3.95 Tbit/cm²²). However, slow read and write times for memories this large seem to limit this technology to hard drive replacements as opposed to high-speed RAM-like uses, although to a very large degree the same is true of flash as well.

===FeFET memory===