Memory speed question

[EOZ]

Maybe someone remembers how to calculate average memory latency ? To these both memory kits.

1. DDR4 2400 CL14-16-16-31
2. DDR4 3000 CL16-18-18-36

So which one has less final latency ?

[just_dave]

3000MHz will be better for Ryzen, Infinity Fabric needs high speed RAM to fix latency between the cores.

Fix the text for black theme

[pyrojoe34]

The math is easy to do.

 

CL / (Frequency / 2) = Latency

 

CL is latency in # of cycles

Frequency in Mhz (divided by two since it is DDR) is million cycles per second

This equation gives latency in microseconds, multiply by 1000 to get nanoseconds.

 

So...

1. 11.7ns

2. 10.7ns

 

So the 3000Mhz has a lower latency, however, that's not the only important metric. It can also do many more cycles per second so it would be the better option in most uses anyway (especially when talking about Ryzen). That doesn't mean that if the latency was higher it would not still be the better option. My point is don't worry too much about latency and frequency only matters in certain use cases (or with systems that use IF like Ryzen).

 

[RyanChase]

The higher number for memory reflects the speed. The bigger the number, the faster it will go, and the less latency you will have!

[EOZ]

Thanks

[EOZ]

.

[pyrojoe34]

32 minutes ago, EOZ said:

Thank you! Just last question how much latency will be on DDR4 2133 CL14-14-14-35 ?

I just gave you the equation... plug in the numbers...

 

Just don't use latency as your only way to choose RAM... getting 2133Mhz RAM just because it has a lower latency than 3000Mhz RAM would be a poor choice...