GDDR6X

GDDR6X is a type of graphics memory in the GDDR family, designed to provide higher bandwidth than its predecessor GDDR6. It was introduced around 2020–2021 by memory manufacturers Samsung Electronics and Micron Technology as an enhanced variant intended for high-performance graphics cards. Like GDDR6, it uses a similar physical form factor and interface, but it relies on new signaling techniques to achieve faster data transfer.

A defining technical feature of GDDR6X is the use of PAM4 signaling, which encodes two bits per symbol and enables higher data rates per clock cycle than NRZ signaling used in GDDR6. This approach allows significantly higher data rates per pin, with commercial implementations typically reaching about 19.5 to 21 Gbps per pin, depending on the device and process. The resulting memory bandwidth depends on the GPU’s memory bus width and configuration.

GDDR6X has been deployed primarily in Nvidia’s high-end RTX 30-series graphics cards. Examples include the RTX 3080 (10 GB of GDDR6X), the RTX 3080 Ti (12 GB), and the RTX 3090 and RTX 3090 Ti (both 24 GB). AMD’s RDNA 2 lineup uses GDDR6 rather than GDDR6X. The memory chips are supplied by Samsung and Micron, reflecting a specialized, performance-oriented deployment rather than a broad, mainstream adoption.

Power and design considerations accompany the higher speeds of GDDR6X, with increased power demands and stricter signal integrity requirements. While the technology provides substantial bandwidth advantages, its use is tied to specific GPU architectures and market segments.