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Memory Latency Cycles Calculator

Work out memory latency cycles instantly with clear inputs, formula shown and shareable results.

About Memory Latency Cycles Calculator

DRAM CAS latency in nanoseconds is the cycle count times the memory clock period, and that has barely improved across generations — CL36 at 3200 MHz is 11.25 ns, much the same as CL9 at 800 MHz. Adding controller and interconnect overhead gives the latency the CPU actually sees.

Formula

Memory latency

CAS ns = CL / memory clock; total = CAS ns + controller overhead; CPU cycles = ns x CPU GHz

Worked example

With the default values below, Memory Latency Cycles Calculator returns Latency in CPU cycles of 130.5. Change any input above and every figure here is recalculated in your browser.

Inputs used

CPU clock
3.6 GHz
CAS latency
36 cycles
Memory clock
3,200 MHz
Controller and interconnect overhead
25 ns

Results

Latency in CPU cycles
130.5 cycles
Latency
36.25 ns
DRAM CAS latency
11.25 ns
CPU cycles per memory cycle
1.13 x

Step by step

  1. 1Values used
  2. 2Memory latency
  3. 3Latency in CPU cycles= 130.5 cycles
  4. 4Latency= 36.25 ns
  5. 5DRAM CAS latency= 11.25 ns
  6. 6CPU cycles per memory cycle= 1.13 x

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why has DRAM latency not improved?

Because latency is set by the sense amplifier and array physics, not the interface. Each generation raises bandwidth by widening and speeding the bus, leaving array access time roughly constant.

Why do CPU cycles of latency keep rising?

The CPU clock has risen faster than memory latency has fallen, so the same nanoseconds cost more cycles — the memory wall.

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