memory. GDDR6X Micron developed GDDR6X in close collaboration with Nvidia. GDDR6X SGRAM had not been standardized by JEDEC yet. Nvidia is Micron's only GDDR6X launch partner. GDDR6X offers increased per-pin bandwidth between 19–21 Gbit/s with PAM4 signaling, allowing two bits per symbol to be transmitted and replacing earlier NRZ (non return to zero, PAM2) coding that provided only one bit per symbol, thereby limiting the per-pin bandwidth of GDDR6 to 16 Gbit/s. The first graphics cards to use GDDR6X are the Nvidia GeForce RTX 3080 and 3090 graphics cards. PAM4 signalling is not new but it costs more to implement, partly because it requires more space in chips and is more prone to signal-to-noise ratio (SNR) issues, which mostly limited its use to high speed networking (like 200G Ethernet). GDDR6X consumes 15% less power per transferred bit than GDDR6, but overall power consumption is higher since GDDR6X is faster than GDDR6. On average, PAM4 consumes less power and uses fewer pins than differential signalling while still being faster than NRZ. GDDR6X is thought to be cheaper than High Bandwidth Memory. GDDR6W Samsung announced the development of GDDR6W on November 29, 2022. Its improvements over GDDR6 are: Higher per pin transmission rate of 22 GT/s Doubling per package capacity from 16 Gb to 32 Gb Double the I/O pins from 32 to 64 36% lower thickness (0.7 mm down from 1.1 mm by using Fan-Out Wafer-Level Packaging (FOWLP) See also List of interface bit rates References SDRAM South Korean inventions