AMD EPYC has 12 channel, 24 on dual socket. AMD sell machines with 2 (consumer), 4 (threadripper), 6 (dense edge), 8 (threadripper pro) and 12 memory channels (EPYC high end). Next generation EPYC will have 16 channels. Roughly if you look at the AMD options, they give you 2 memory channels per 16 cores. CPUs tend to be somewhat limited in what bandwidth they can use, eg on Apple Silicon you cant actually consume all the memory bandwidth on the wider options just on the CPUs, its mainly useful for the GPU. DDR5 was double speed of DDR4, and speeds have been ramping up too, so there have been improvements there.