Electronic Design

Graphics DRAM Zooms At 6.4-Gbyte/s Aggregate Throughput

A throughput of 1.6 Gbits/s per data pin highlights the GDDR3 graphics DRAM. It represents an extension to the second-generation double-data-rate SDRAM technology. Developed by Micron Technology Inc., the GDDR3 homes in on high-performance graphics subsystems that use point-to-point connections between the graphics controller and the memories. Other applications involve high-bandwidth networking systems.

Organized as 8 Mwords by 32 bits, the 256-Mbit memory delivers an aggregate throughput of 6.4 Gbytes/s, which makes it the fastest high-density memory available today. It operates at rates about 50% faster than other memories used by graphics controllers at about half the power (approximately 2 W/chip) versus DDR2 SDRAMs. This reduces the overall power consumption of a graphics card. The GDDR3 memory bus includes on-chip 1.8-V termination, and both the bus and core of the chip operate from a 1.8-V supply.

The memory features single-ended Read and Write strobes and per-byte read-data and write-data strobe signals. A single resistor can be used to set the programmable impedance of the output driver, optimizing the interface to the graphics controller.

Available in a 12- by 13-mm 135-ball BGA package, the GDDR3 uses a single pin to control the pinout to provide both the standard pinout and a mirrored version of the pinout. Therefore, two chips can be mounted clamshell style, one on each side of a pc-board, without complex routing of the data signals.

Micron Technology Inc.

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