GDDR4
Encyclopedia
GDDR4 SDRAM is a type of graphics card memory specified by the JEDEC
Semiconductor Memory Standard. It is a rival medium to Rambus's
XDR DRAM
. GDDR4 is based on DDR3 SDRAM
technology and was intended to replace the DDR2
-based GDDR3
, but it ended up being replaced by GDDR5
within a year.
was increased from 4 to 8 bits. The maximum number of memory banks for GDDR4 has been increased to 8. To achieve the same bandwidth as GDDR3 SDRAM, the GDDR4 core runs at half the performance of a GDDR3 core of the same raw bandwidth. Core voltage was decreased to 1.5 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 least 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 9 pins is limited to 4. 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 Gbit/s, it uses 45% less power when compared to GDDR3 chips running at 2.0 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.
' Radeon X1950 XTX
and Radeon HD 2900 XT and 2600 XT
video cards. GDDR4 is intended to achieve clock rates as high as 1.4 GHz (2.8 GBit/s). However, Samsung
had aimed to increase GDDR4 to effective clock rates as high as 1.6 GHz (3.2 GBit/s, at higher voltage) and was rumoured to have implemented this improvement into some of the Radeon HD 2900 XT cards .
Graphics cards incorporating GDDR4 memory are now available for purchase with a clock rate of around 1.0 GHz to 1.1 GHz. Samsung was quoted saying they would have 1.6 GHz GDDR4 ready for market as early as July, 2006. NVIDIA
was also rumored to have had plans of utilizing the memory on newer revisions of their current-generation GeForce 8-Series
GPUs, but instead NVIDIA has used GDDR3
in all of the GeForce 8 cards. Adoption of GDDR4 has been minimal compared to GDDR3 which is still extremely prevalent in most mainstream Graphics cards. Some graphics vendors are adopting DDR3 instead of moving to GDDR4 or 5.
The video memory manufacturer Qimonda
(formerly Infineon Memory Products division) has stated it will "skip" the development of GDDR4, and move directly to GDDR5
.
JEDEC
The JEDEC Solid State Technology Association, formerly known as the Joint Electron Devices Engineering Council , is an independent semiconductor engineering trade organization and standardization body...
Semiconductor Memory Standard. It is a rival medium to Rambus's
Rambus
Rambus Incorporated , founded in 1990, is a technology licensing company. The company became well known for its intellectual property based litigation following the introduction of DDR-SDRAM memory.- History :...
XDR DRAM
XDR DRAM
XDR DRAM or extreme data rate dynamic random access memory is a high-performance RAM interface and successor to the Rambus RDRAM it is based on, competing with the rival DDR2 SDRAM and GDDR4 technology. XDR was designed to be effective in small, high-bandwidth consumer systems, high-performance...
. GDDR4 is based on DDR3 SDRAM
DDR3 SDRAM
In computing, DDR3 SDRAM, an abbreviation for double data rate type three synchronous dynamic random access memory, is a modern kind of dynamic random access memory with a high bandwidth interface. It is one of several variants of DRAM and associated interface techniques used since the early 1970s...
technology and was intended to replace the DDR2
DDR2 SDRAM
DDR2 SDRAM is a double data rate synchronous dynamic random-access memory interface. It supersedes the original DDR SDRAM specification and has itself been superseded by DDR3 SDRAM...
-based GDDR3
GDDR3
Graphics Double Data Rate 3 is a graphics card-specific memory technology, designed by ATI Technologies with the collaboration of JEDEC.It has much the same technological base as DDR2, but the power and heat dispersal requirements have been reduced somewhat, allowing for higher performance memory...
, but it ended up being replaced by GDDR5
GDDR5
GDDR5 SDRAM is a type of high performance DRAM graphics card memory designed for computer applications requiring high bandwidth...
within a year.
History
- On October 26, 2005, Samsung announced the development of 256-MibMebibitThe mebibit is a multiple of the bit, a unit of digital information storage, prefixed by the standards-based multiplier mebi , a binary prefix meaning 220...
GDDR4 memory running at 2.5 Gbit/s. Samsung also revealed plans to sample and mass-produce GDDR4 SDRAM rated at 2.8 Gbit/s per pin.
- On February 14, 2006, Samsung announced the development of 32-bit 512-MiBit GDDR4 SDRAM capable of transferring 3.2 Gbit/s per pin, or 12.8 GB/s for the module.
- On July 5, 2006, Samsung announced the mass-production of 32-bit 512-Mibit GDDR4 SDRAM rated at 2.4 Gbit/s per pin, or 9.6 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.
- On February 9, 2007, Samsung announced mass-production of 32-bit 512-Mbit GDDR4 SDRAM, rated at 2.8 Gbit/s per pin, or 11.2 GB/s per module. This module will be available for the latest version of AMD cards.
- On February 23, 2007, Samsung announced 32-bit 512-Mibit GDDR4 SDRAM rated at 4.0 Gbit/s per pin or 16 GB/s for the module and expects the memory to appear on commercially-available graphics cards by the end of year 2007.
Technologies
GDDR4 SDRAM introduced DBI (Data Bus Inversion) and Multi-Preamble to reduce data transmission delay. PrefetchPrefetch buffer
A prefetch buffer is a data buffer employed on modern DRAM chips that allows quick and easy access to multiple data words located on a common physical row in the memory....
was increased from 4 to 8 bits. The maximum number of memory banks for GDDR4 has been increased to 8. To achieve the same bandwidth as GDDR3 SDRAM, the GDDR4 core runs at half the performance of a GDDR3 core of the same raw bandwidth. Core voltage was decreased to 1.5 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 least 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 9 pins is limited to 4. This reduces power consumption and ground bounce
Ground bounce
In electronic engineering, ground bounce is a phenomenon associated with transistor switching where the gate voltage can appear to be less than the local ground potential, causing the unstable operation of a logic gate.-Description:...
.
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
CAS Latency
Column Address Strobe latency, or CL, is the delay time between the moment a memory controller tells the memory module to access a particular memory column on a RAM memory module, and the moment the data from given array location is available on the module's output pins...
(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 Gbit/s, it uses 45% less power when compared to GDDR3 chips running at 2.0 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 memory became available with ATI TechnologiesATI Technologies
ATI Technologies Inc. was a semiconductor technology corporation based in Markham, Ontario, Canada, that specialized in the development of graphics processing units and chipsets. Founded in 1985 as Array Technologies Inc., the company was listed publicly in 1993 and was acquired by Advanced Micro...
' Radeon X1950 XTX
Radeon R520
ATI's "R520" core is the foundation for a line of DirectX 9.0c and OpenGL 2.0 3D accelerator X1000 video cards. It is ATI's first major architectural overhaul since the "R300" core and is highly optimized for Shader Model 3.0. The Radeon X1000 series using the core was introduced on October 5,...
and Radeon HD 2900 XT and 2600 XT
Radeon R600
The graphics processing unit codenamed the Radeon R600 is the foundation of the Radeon HD 2000/3000 series and the FireGL 2007 series video cards developed by ATI Technologies...
video cards. GDDR4 is intended to achieve clock rates as high as 1.4 GHz (2.8 GBit/s). However, Samsung
Samsung Group
The Samsung Group is a South Korean multinational conglomerate corporation headquartered in Samsung Town, Seoul, South Korea...
had aimed to increase GDDR4 to effective clock rates as high as 1.6 GHz (3.2 GBit/s, at higher voltage) and was rumoured to have implemented this improvement into some of the Radeon HD 2900 XT cards .
Graphics cards incorporating GDDR4 memory are now available for purchase with a clock rate of around 1.0 GHz to 1.1 GHz. Samsung was quoted saying they would have 1.6 GHz GDDR4 ready for market as early as July, 2006. NVIDIA
NVIDIA
Nvidia is an American global technology company based in Santa Clara, California. Nvidia is best known for its graphics processors . Nvidia and chief rival AMD Graphics Techonologies have dominated the high performance GPU market, pushing other manufacturers to smaller, niche roles...
was also rumored to have had plans of utilizing the memory on newer revisions of their current-generation GeForce 8-Series
GeForce 8 Series
The GeForce 8 Series, is the eighth generation of NVIDIA's GeForce line of graphics processing units. The third major GPU architecture developed at NVIDIA, the GeForce 8 represents the company's first unified shader architecture.-Naming:...
GPUs, but instead NVIDIA has used GDDR3
GDDR3
Graphics Double Data Rate 3 is a graphics card-specific memory technology, designed by ATI Technologies with the collaboration of JEDEC.It has much the same technological base as DDR2, but the power and heat dispersal requirements have been reduced somewhat, allowing for higher performance memory...
in all of the GeForce 8 cards. Adoption of GDDR4 has been minimal compared to GDDR3 which is still extremely prevalent in most mainstream Graphics cards. Some graphics vendors are adopting DDR3 instead of moving to GDDR4 or 5.
The video memory manufacturer Qimonda
Qimonda
Qimonda AG, was a memory company split out of Infineon Technologies on 1 May 2006, to form at the time the second largest DRAM company worldwide, according to the industry research firm Gartner Dataquest...
(formerly Infineon Memory Products division) has stated it will "skip" the development of GDDR4, and move directly to GDDR5
GDDR5
GDDR5 SDRAM is a type of high performance DRAM graphics card memory designed for computer applications requiring high bandwidth...
.