Nope, DDR4-4000 is not "running at 4 GHz". SDRAM 133 ran at 133 MHz, but DDR numbers have always multiplied their frequency by "number of simultaneous transfers

Nope, DDR4-4000 is not "running at 4 GHz". SDRAM 133 ran at 133 MHz, but DDR numbers have always multiplied their frequency by "number of simultaneous transfers" or something like that. (The first DDR multiplied by two - "double data rate".) Wikipedia has a good table for DDR3: https://en.wikipedia.org/wiki/DDR3_SDRAM#JEDEC_standard_modules https://en.wikipedia.org/wiki/DDR3_SDRAM#JEDEC_standard_modu... DDR3-2133 has a 266.67 MHz memory clock, and a 1066.67 MHz bus clock (x 4), and a "data rate" of 2133 "mega-transfers per second". And a bunch of other details, it's complicated. The point is, don't take the "4000" literally. It's complicated. And timings and latency can differ between models of the same "data rate".