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I've been looking over RAM timings today, and one thing I noticed is that, even when considering very high-end DDR4 RAM, the timings are absolutely massive compared to DDR3 - I can buy very cheap DDR3 RAM with 9-9-9-24 timing, but DDR4 RAM (at nearly ten times the cost) might have a timing of 19-24-24-46. I have two questions about this:

  1. Why are the timings so much higher in DDR4?
  2. Does the speed of DDR4 ram overcome the massive timing increases?
Kulahan
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1 Answers1

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1600MHz  9-9-9-24       1.25e-9 seconds per clock tick
CL = (1.25e-9 * 9)   =  1.125e-8 seconds
RtC = (1.25e-9 * 9)  =  1.125e-8 seconds
RtP = (1.25e-9 * 9)  =  1.125e-8 seconds
tRAS =(1.25e-9 * 24) =  3.0e-8 seconds

4266MHz 19-24-24-46     4.688e-10 seconds per clock tick
CL =  (4.688e-10 * 19)  = 8.907e-9 seconds
RtC = (4.688e-10 * 24)  = 1.125e-8 seconds
RtP = (4.688e-10 * 24)  = 1.125e-8 seconds
tRAS = (4.688e-10 * 46) = 2.156e-8 seconds

So on timings, the DDR4 is the clear winner, being at worst equal to the DDR3 latencies, and at best is in an different order of magnitude.

Frank Thomas
  • 37,476