View source for GDDR4 SDRAM

{{short description|Type of graphics card memory}}
{{about|DDR graphics RAM (SGRAM)|non-graphics (dynamic) DDR memory|DDR4 SDRAM}}
{{Infobox memory
| abbr       = GDDR4 SDRAM
| name       = Graphics Double Data Rate 4 Synchronous Dynamic Random-Access Memory
| image      = 
| caption    = 
| developer  = [[JEDEC]]
| type       = [[Synchronous dynamic random-access memory]]
| generation = 4th generation
| release    = 
| standards  =
| clock_rate = 
| cycle_time = 
| prefetch   = 
| bus_clock_rate =
| transfer_rate  = 
| bandwidth = 
| voltage   = 
| predecessor = [[GDDR3 SDRAM]]
| successor = [[GDDR5 SDRAM]]
}}
'''GDDR4 SDRAM''', an abbreviation for '''Graphics Double Data Rate 4 Synchronous Dynamic Random-Access Memory''', is a type of [[graphics card]] [[Random access memory|memory]] (SGRAM) specified by the [[JEDEC]] Semiconductor Memory Standard.<ref>{{cite web|url=http://www.jedec.org/standards-documents/results/SGRAM|title=Standards & Documents Search: sgram|publisher=www.jedec.org|access-date=9 September 2013}}</ref><ref>{{cite web|url=http://www.jedec.org/standards-documents/results/GDDR4|title=Standards & Documents Search: gddr4|publisher=www.jedec.org|access-date=9 September 2013}}</ref> It is a rival medium to [[Rambus|Rambus's]] [[XDR DRAM]]. GDDR4 is based on [[DDR3 SDRAM]] technology and was intended to replace the [[DDR2 SDRAM|DDR2]]-based [[GDDR3]], but it ended up being replaced by [[GDDR5]] within a year.

==History==
* On October 26, 2005, [[Samsung Electronics|Samsung]] announced that it developed the first GDDR4 memory, a 256-[[Mebibit|Mbit]] chip running at 2.5&nbsp;[[Gibibit|Gbit/s]]. Samsung also revealed plans to sample and mass-produce GDDR4 SDRAM rated at 2.8&nbsp;Gbit/s per pin.<ref>{{cite web |title=Samsung Electronics Develops Industry's First Ultra-Fast GDDR4 Graphics DRAM |url=https://www.samsung.com/semiconductor/insights/news-events/samsung-electronics-develops-industrys-first-ultra-fast-gddr4-graphics-dram/ |website=[[Samsung Semiconductor]] |publisher=[[Samsung]] |access-date=8 July 2019 |date=October 26, 2005}}</ref>
* In 2005, [[Hynix]] developed the first 512-Mbit GDDR4 memory chip.<ref name="hynix2000s">{{cite web |title=History: 2000s |url=https://www.skhynix.com/eng/about/history2000.jsp |website=[[SK Hynix]] |access-date=8 July 2019 |archive-date=6 August 2020 |archive-url=https://web.archive.org/web/20200806163108/https://www.skhynix.com/eng/about/history2000.jsp |url-status=dead }}</ref>
* On February 14, 2006, Samsung announced the development of 32-bit 512-Mbit GDDR4 SDRAM capable of transferring 3.2&nbsp;Gbit/s per pin, or 12.8&nbsp;GB/s for the module.<ref>[http://www.samsung.com/Products/Semiconductor/News/GraphicsMemory/category_GraphicsMemory_20060214_0000233753.htm Samsung Develops Ultra-fast Graphics Memory: A More Advanced GDDR4 at Higher Density]</ref>
* On July 5, 2006, Samsung announced the mass-production of 32-bit 512-Mbit GDDR4 SDRAM rated at 2.4&nbsp;Gbit/s per pin, or 9.6&nbsp;GB/s for the module. Although designed to match the performance of XDR DRAM on high-pin-count memory, it would not be able to match XDR performance on low-pin-count designs.<ref>[https://web.archive.org/web/20060706142817/http://www.tgdaily.com/2006/07/05/samsung_gddr4/ Samsung sends GDDR4 graphics memory into mass production]</ref>
* On February 9, 2007, Samsung announced mass-production of 32-bit 512-Mbit GDDR4 SDRAM, rated at 2.8&nbsp;Gbit/s per pin, or 11.2&nbsp;GB/s per module. This module was used for some [[AMD]]-[[ ATI Technologies|ATI]] cards.<ref>{{cite web |url=http://www.theinquirer.net/default.aspx?article=37559 |title=Samsung releases fastest GDDR-4 SGRAM |work=[[The Inquirer]] |url-status=unfit |archive-url=https://web.archive.org/web/20070212033434/http://theinquirer.net/default.aspx?article=37559 |archive-date=2007-02-12}}</ref>
* On February 23, 2007, Samsung announced 32-bit 512-Mbit GDDR4 SDRAM rated at 4.0&nbsp;Gbit/s per pin or 16&nbsp;GB/s for the module and expects the memory to appear on commercially available graphics cards by the end of year 2007.<ref>[https://web.archive.org/web/20070225083354/http://www.tgdaily.com/2007/02/23/samsung_gddr/ Samsung accelerates graphics memory to 2000 MHz]</ref>

==Technologies==
GDDR4 SDRAM introduced DBI (Data Bus Inversion) and Multi-Preamble to reduce data transmission delay. [[Prefetch buffer|Prefetch]] was increased from 4 to 8 bits. The maximum number of memory banks for GDDR4 has been increased to 8. Core voltage was decreased to 1.5&nbsp;V.

Data Bus Inversion adds an additional [[active-low]] DBI# pin to the address/command bus and each byte of data.  If there are at more than four 0 bits in the data byte, the byte is inverted and the DBI# signal transmitted low.  In this way, the number of 0 bits across all nine pins is limited to four.<ref>{{cite conference
 |title=DDR4 Mini Workshop
 |conference=Server Memory Forum 2011
 |year=2011
 |first=J.S. |last=Choi
 |url=https://www.jedec.org/sites/default/files/JS_Choi_DDR4_miniWorkshop.pdf#page=9
}}  This presentation is about DDR4 rather than GDDR4, but both use data bus inversion.</ref>{{Rp|9}}  This reduces power consumption and [[ground bounce]].

On the signaling front, GDDR4 expands the chip I/O buffer to 8 bits per two cycles, allowing for greater sustained bandwidth during burst transmission, but at the expense of significantly increased [[CAS latency]] (CL), determined mainly by the double reduced count of the address/command pins and half-clocked DRAM cells, compared to GDDR3. The number of addressing pins was reduced to half that of the GDDR3 core, and were used for power and ground, which also increases latency. Another advantage of GDDR4 is power efficiency: running at 2.4&nbsp;Gbit/s, it uses 45% less power when compared to GDDR3 chips running at 2.0&nbsp;Gbit/s.

In Samsung's GDDR4 SDRAM datasheet, it was referred as 'GDDR4 SGRAM', or 'Graphics Double Data Rate version 4 Synchronous Graphics RAM'. However, the essential block write feature is not available, so it is not classified as [[SGRAM]].

==Adoption==
The video memory manufacturer [[Qimonda]] (formerly [[Infineon]] Memory Products division) has stated it will "skip" the development of GDDR4, and move directly to [[GDDR5]].<ref>[http://news.softpedia.com/news/Qimonda-Plans-GDDR5-50282.shtml Softpedia report]</ref>

==See also==
* [[List of interface bit rates]]

==References==
{{reflist}}

==External links==
* [https://web.archive.org/web/20150128201329/http://www.xbitlabs.com/news/memory/display/20040505122429.html X-Bit Labs (GDDR4 closing in)]
* [https://web.archive.org/web/20141228073217/http://www.xbitlabs.com/news/memory/display/20060214062714.html X-Bit Labs (GDDR4 achieving 3.2 GHz)]
* [https://web.archive.org/web/20131203095557/http://www.dailytech.com/article.aspx?newsid=3781 DailyTech (ATI X1950 Now September 14)]
* [https://web.archive.org/web/20131203100000/http://www.dailytech.com/article.aspx?newsid=3446 DailyTech (ATI Radeon X1950 Announced)]
* [https://web.archive.org/web/20131203100546/http://www.dailytech.com/article.aspx?newsid=3162 (Samsung Shipping Production GDDR4)]
* [http://www.samsung.com/Products/Semiconductor/News/GraphicsMemory/category_GraphicsMemory_20060705_0000273583.htm Samsung Mass Producing Most Advanced Graphics Memory: GDDR4, press release]

{{DRAM}}
{{Graphics Processing Unit}}

{{DEFAULTSORT:Gddr4}}
[[Category:SDRAM]]
[[Category:South Korean inventions]]