Samsung recently confirmed that GDDR7 RAM uses PAM-3 signaling (Pulse Amplitude Modulation 3-level). This will help it give future graphics cards double the data rate of GDDR6.
https://www.techspot.com/news/96896-samsung-confirms-wants-gddr7-ram-reach-36gbps-pam.html?utm_source=dlvr.it&utm_medium=blogger
https://www.techspot.com/news/96896-samsung-confirms-wants-gddr7-ram-reach-36gbps-pam.html?utm_source=dlvr.it&utm_medium=blogger