my old p4 has DDR-400Mhz. 2GB of 400MHz CL1.5! That was a big deal for its time.
my core2Duo has DDR2-800Mhz CL6 or 7 can't remember now.
my old i7-870 machine 1600 CL9/1866 CL10/2133MHz CL11 (as XMP ratings) to suit the CPU overclock I'm using at the time
my 3900x machine 32GB 3600MHz CL16 (as XMP rating) It's BDie so I should probably push it and see what it will do