Higher clock speed or lower latency

happyguy82 · Jan 24, 2017

Hello all,

Similar articles on this subject seem to cover the older DDR3 memories. The DDR4 playing field seems to be a little different, thus I would like some advice on this specific example.

Which would be a better option of the following two?

Btw, assume the chipset is Z270 and CPU is 7700K. Thank you.

1) [Trident Z] F4-3400C16Q-64GTZ

DDR4-3400 (PC4-27200)
64GB (16GBx4)
CL16-16-16-36
1.35 Volt

2) [Trident Z RGB] F4-3600C17Q-64GTZR

DDR4-3600 (PC4-28800)
64GB (16GBx4)
CL17-19-19-39
1.35 Volt

I don't now if I'm doing this right but:

1) 3,400 / 16 = 212.5

2) 3,600 / 19 = 189.4

The math implies that the 3,400 Mhz with lower latency achieves more operations per second, thus Option 1 seems more logical. I'm not sure whether this analysis is flawed.

Please advise.

Thank you.

Dark Lord of Tech · Jan 24, 2017

You may also need a small OC to run the higher speed modules at full spec.

http://www.crucial.com/usa/en/memory-performance-speed-latency
Great read here ^

greens · Jan 24, 2017

happyguy82 :

(CL/(freq-in-MHZ) * 1000) = timing in ns

(16/3400 * 1000) = 4.705
(17/3600* 1000) = 4.722
Very close. The lower CL actually has a larger impact on speeds.
(14/3200*1000) = 4.375

Really as long as the actual timing comes out below 5 - you're in a good place.

The closer you can get to 4 the better. I don't believe DDR4 will be going below 4ns any time soon.

happyguy82 · Jan 24, 2017

Hello,

Thanks and sorry I'm a bit confused by the 1st bit as I thought XMP takes care of OC automatically?

Thanks for the URL, I'll read up over dinner.

Cheers.

happyguy82 · Jan 24, 2017

greens :

happyguy82 :

(CL/(freq-in-MHZ) * 1000) = timing in ns

(16/3400 * 1000) = 4.705
(17/3600* 1000) = 4.722
Very close. The lower CL actually has a larger impact on speeds.
(14/3200*1000) = 4.375

Really as long as the actual timing comes out below 5 - you're in a good place.

The closer you can get to 4 the better. I don't believe DDR4 will be going below 4ns any time soon.

Hello mate,

Thanks for the correction. Ahh this is even more confusing because the fastest (3200 Mhz) based on your calculation appears to be the cheapest of the 3; so why would one buy higher speed RAM modules?

Thanks again.

Dark Lord of Tech · Jan 24, 2017

Not always , sometimes a small OC on the CPU is needed to run the higher rated modules at FULL spec, usually it will happen at 3000 and up. NOT always , but be aware of this.

greens · Jan 24, 2017

happyguy82 :

greens :

Hello mate,

Thanks for the correction. Ahh this is even more confusing because the fastest (3200 Mhz) based on your calculation appears to be the cheapest of the 3; so why would one buy higher speed RAM modules?

Thanks again.

Not all 3200 has a CAS/CL of 14, usually it is higher.
I love my Team Dark Pros though.

happyguy82 · Jan 24, 2017

Ahh OK so then how would I know whether it's required? How can I tell whether it's running at full spec and what does that mean? Thanks again.

greens · Jan 24, 2017

Enable XMP, see that it has the correct clock - lets say 3200.

PC boots up, doesn't crash - then it worked.
PC doesn't boot, or boots but crashes- you need to adjust some stuff.

You can use HWMonitor to see what things are running at from within windows.

Dark Lord of Tech · Jan 24, 2017

Try setting the XMP after build is up and running. You will know if it doesn't take. Sometimes it's fine.

happyguy82 · Jan 24, 2017

greens :

happyguy82 :

greens :

Hello mate,

Thanks for the correction. Ahh this is even more confusing because the fastest (3200 Mhz) based on your calculation appears to be the cheapest of the 3; so why would one buy higher speed RAM modules?

Thanks again.

Not all 3200 has a CAS/CL of 14, usually it is higher.
I love my Team Dark Pros though.

Hello,

Thanks again. So you're saying given your example the 3,200 would be the fastest option of the 3 right?

Thanks.

Dark Lord of Tech · Jan 24, 2017

Yes with the SPEED and lower CAS , it should be , but it the real world you would never notice a difference.

happyguy82 · Jan 24, 2017

Thank you everyone

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Higher clock speed or lower latency

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