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How do you calculate the relative performance of PC RAM?

For example, what is the relative performance of the following:

  • G.Skill Ripjaws Z 8 x 4GB Kit, DDR3-2133, CL9-11-10-28@1.65V

  • G.Skill Ripjaws Z 4 x 8GB Kit, DDR3-1600, CL10-10-10-30@1.5V

If it's relevant, when they are used in a top of the line ASUS Rampage IV Extreme motherboard and Intel i7 3960X?

By performance, I mean relative:

  1. read latency
  2. write latency
  3. read bandwidth
  4. write bandwidth

Please include working. (I mean how did you arrive at the figures based on timing and DDR3-speed)

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1 Answer 1

up vote 1 down vote accepted

Exact calculations are extremely complex and depend on the exact access pattern, as well as the internal configuration of the memory module ( generally not listed in the specs ). The simple calculation for latency is to divide it by the frequency, so:

9 / 2,133,000,000 = 4.219 ns
10 / 1,600,000,000 = 6.25 ns

And the simplistic calculation for throughput is to multiply the frequency by the word size, which is 8 bytes:

2133 * 8 = 17,064 MB/s
1600 * 8 = 12,800 MB/s
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