DDR memory speeds
“Like the ticking of a clock, each tick represents a single hertz or cycle (the opening and closing of a transistor gate in this case).
A speed of 1Hz, for example, is one cycle per second; 2Hz is two per second; a MHz is 1,000,000 cycles per second; you get the picture.
The problem is when DDR (or double data rate) RAM came on the scene, it changed how data transfers were registered. Instead of only actuating once on the rise of each clock cycle, it could now also process an additional operation on the fall of that same clock cycle, effectively doubling the rate at which the DIMM could process data.
The figure for accurate measurement of data transfer requests then shifted from MHz to MT/s to adjust for this change, despite the fact that memory still operated at the same frequency.
However, marketing apparently didn’t get that memo, because many companies, in a bid to tout it as the next big thing, ignored the MT/s figure, instead referring it as MHz, while modern day memory quoted at 2,400MHz, for instance, only operates at half that frequency.”
APC Mag, Apr 2018, Issue 453