Editing Pulse-amplitude modulation (section)

===GDDR6X===
[[GDDR6 SDRAM|GDDR6X]], developed by Micron<ref>{{cite web |title=Doubling I/O Performance with PAM4 - Micron Innovates GDDR6X to Accelerate Graphics Memory |url=https://media-www.micron.com/-/media/client/global/documents/products/technical-marketing-brief/gddr6x_pam4_2x_speed_tech_brief |website=Micron |access-date=11 September 2020}}</ref> and Nvidia and first used in the [[GeForce 30 series|Nvidia RTX 3080 and 3090]] graphics cards, uses PAM-4 signaling to transmit 2 bits per clock cycle without having to resort to higher frequencies or two channels or lanes with associated transmitters and receivers, which may increase power or space consumption and cost. Higher frequencies require higher bandwidth, which is a significant problem beyond 28&nbsp;GHz when trying to transmit through copper. PAM-4 costs more to implement than earlier NRZ (non return to zero, PAM-2) coding partly because it requires more space in integrated circuits, and is more susceptible to SNR (signal to noise ratio) problems.<ref>{{Cite web|url=https://www.anandtech.com/show/15978/micron-spills-on-gddr6x-pam4-signaling-for-higher-rates-coming-to-nvidias-rtx-3090|title=Micron Spills on GDDR6X: PAM4 Signaling For Higher Rates, Coming to NVIDIA's RTX 3090|first=Ryan|last=Smith|website=AnandTech.com}}</ref><ref>{{Cite web|url=https://www.edn.com/the-fundamentals-of-pam4/|title=EDN - The fundamentals of PAM4|first=David|last=Maliniak|date=January 14, 2016}}</ref>