Antone know a chart with True CAS latency for DDR4?

The latency formulas for DDR4 are the same as DDR3, so you could easily just calculate them yourself as needed:

Single Word Read Latency:
CL * 2000 /DDRrate

Four Word Read Latency:
CL * 2000 / DDRrate + (3*1000 / DDRrate)

Eight Word Read Latency:
CL * 2000 / DDRrate + (7*1000 / DDRrate)

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So for example, with the DDR4-3600 CAS18 which [H] tested in their i7-6700K review, you would get:

Single Word Read Latency:
18 * 2000 / 3600 = 10ns

Four Word Read Latency:
18 * 2000 / 3600 + (3000 / 3600) = 10.83ns

Eight Word Read Latency:
18 * 2000 / 3600 + (7000 / 3600) = 11.94ns

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Right now, the lowest latency stock kits seem to be DDR4-3466 CAS16 at the following, which still is rather mediocre against fast DDR3:

Single Word Read Latency: 9.23ns
Four Word Read Latency: 10.1ns
Eight Word Read Latency: 11.25ns

Though with an underclock/overclock, I'd expect you could drop down latencies down at least another 0.5ns at still decent speeds above DDR3.
 
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yea thanks for the fast reply. About an hour or two ago i was looking through the crucial pages and no jut the charts and noticed the formula was actually in there.

they skip some of the math your doing so could you explain that 2000 number?
 
I pulled that formula using the 2000 number from an Anandtech article awhile back, since I found it handy that it used the DDR rate directly in calculations.

The common formula you may see mentioned is (CAS * 1000 / MHz) or (CAS / MHz * 1000) which yields identical results yet expects MHz (DDRrate / 2).
 
Cyberbeing said:
I pulled that formula using the 2000 number from an Anandtech article awhile back, since I found it handy that it used the DDR rate directly in calculations.

The common formula you may see mentioned is (CAS * 1000 / MHz) or (CAS / MHz * 1000) which yields identical results yet expects MHz (DDRrate / 2).
Click to expand...

thanks
 
then you have where theoretical speed meats actual
but this is all on skylake which is probably tuned to ddr4 performance so ddr3 may do better on haswell
sky%20r_zpsepkfhqdl.jpg
 
Nice chart
So it seems for ddr4 the sweet spot for 6700k seems to be 2666cl15 to 3000cl15 or anything higher doesn't seem to do produce and real gains. How about filling about all 4 memory slots does it matter what speed memory is being used ?
 
the_real_7 said:
Nice chart
So it seems for ddr4 the sweet spot for 6700k seems to be 2666cl15 to 3000cl15 or anything higher doesn't seem to do produce and real gains. How about filling about all 4 memory slots does it matter what speed memory is being used ?
Click to expand...

this is response times and not necessarily throughput. Yes the Arma 3 is throughput in a sense but its one example of thousands of possible real world work scenarios. It all depends on what your work is. If you have quad channel and 8+ cores you might find that the 3600 is worth the premium.

I wonder how that chart changes with 8-16 core CPUs. I am concerned with RAMdisks not for just games but also Photoshop and other programs. Snappiness is crucial to me.
 
dasa said:
sorry forgot the link to go with that image it has some bandwidth tests aswell
http://www.hardware.fr/articles/940-5/cpu-ddr4-vs-ddr3-pratique.html

how much they help it is with the real world things your using it for i dont know
i would just get the fastest available before price blows out for the premium sticks as i cant see them being worth the price
Click to expand...

Yep :D Thats what i always do go for fastest lowest latency and largest capacity before premiums start to kick in.

Thanks for link. I'll take a look at it when I start to look at DDR4 more closely!
 
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