I'm not aware of anyone actually going to use pam8 or 16 with high-frequency links. The signal integrity is a mess and the corresponding FEC requirements undo a

I'm not aware of anyone actually going to use pam8 or 16 with high-frequency links. The signal integrity is a mess and the corresponding FEC requirements undo all the benefits. I suppose a relatively high-speed chip-to-chip standard in use within consumer computers today is GDDR. If you want something with serdes then it's obviously PCIe, which has been using NRZ and now PAM4. Then there's Interlaken which has been around for yonks in HPC and networking. More recently NVLink also. None of these point-to-point serdes solutions can give you latency anywhere near DDR. And when they get to 200Gbps, copper backplanes are dead. It's cable now, and optical is coming. On the PCB, copper channels are thankfully holding out.