GDDR3 SDRAM

This article is about Graphics DDR3 SDRAM (GDDR3 SDRAM). For DDR3 SDRAM, seeDDR3 SDRAM.

GDDR3 SDRAM(Graphics Double Data Rate 3 SDRAM) is a type ofDDR SDRAMspecialized forgraphics processing units(GPUs) offering less access latency and greater device bandwidths.Its specification was developed byATI Technologiesin collaboration withDRAMvendors includingElpida Memory,Hynix Semiconductor,Infineon(laterQimonda) andMicron.It was later adopted as aJEDECstandard.

GDDR3 SDRAM
Graphics Double Data Rate 3 Synchronous Dynamic Random-Access Memory

Type ofRAM
GDDR3 chips on aAMD Radeon HD 4670
Developer	JEDEC
Type	Synchronous dynamic random-access memory
Generation	3rd generation
Predecessor	GDDR2 SDRAM
Successor	GDDR4 SDRAM

A Samsung GDDR3 256MBit package

Inside a Samsung GDDR3 256MBit package

Overview

It has much the same technological base asDDR2,but the power and heat dispersal requirements have been reduced somewhat, allowing for higher performance memory modules, and simplified cooling systems. GDDR3 is not related to theJEDECDDR3specification. This memory uses internalterminators,enabling it to better handle certain graphics demands. To improve throughput, GDDR3 memory transfers 4bitsof data per pin in 2clock cycles.

The GDDR3 interface transfers two 32 bit wide data words per clock cycle from the I/O pins. Corresponding to the 4n-prefetch a single write or read access consists of a 128 bit wide, one-clock-cycle data transfer at the internal memory core and four corresponding 32 bit wide, one-half-clock-cycle data transfers at the I/O Pins. Single-ended unidirectional Read and Write Data strobes are transmitted simultaneously with Read and Write data respectively in order to capture data properly at the receivers of both the Graphics SDRAM and the controller.Data strobesare organized per byte of the 32 bit wide interface.

Commercial implementation

Despite being designed byATI,the first card to use the technology wasnVidia'sGeForce FX5700 Ultra in early 2004, where it replaced theGDDR2chips used up to that time. The next card to use GDDR3 was nVidia'sGeForce 6800 Ultra,where it was key in maintaining reasonable power requirements compared to the card's predecessor, theGeForce 5950 Ultra.ATI began using the memory on itsRadeon X800cards. GDDR3 wasSony's choice for thePlayStation 3gaming console's graphics memory, although itsnVidiabased GPU is also capable of accessing the main system memory, which consists ofXDR DRAMdesigned byRambus Incorporated(Similar technology is marketed by nVidia asTurboCachein PC platform GPUs).Microsoft'sXbox 360has 512 MB of GDDR3 memory.Nintendo'sWiialso contains 64 MB of GDDR3 memory.

Advantages of GDDR3 over DDR2

• GDDR3's strobe signal unlikeDDR2 SDRAMis unidirectional & single-ended (RDQS, WDQS). This means there is a separate read and write data strobe allowing for a quicker read to write ratio than DDR2.
• GDDR3 has a hardware reset capability allowing it to flush all data from memory and then start again.
• Lower voltage requirements leads to lower power requirements, and lower heat output.
• Higher clock frequencies, due to lower heat output, this is beneficial for increasedthroughputand more precise timings.

See also

• List of interface bit rates

References

• Gregory Agostinelli."Method and Apparatus for fine tuning a memory interface".US PATENT OFFICE.

External links

• JEDEC Standard 3.11.5.7 - GDDR3 Specific SGRAM Functions