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RAM Speed VS Latency

Florre
Level 7
What is more important ram speed or latency?

2400mhz with latency 10-11 or 1866mhz with latency 9?
CPU Intel i7 5960X@ 4.5Ghz
RAM Corsair Dominator Platinum 32GB 2400mhz
GPU 2 X EVGA GTX 980 in SLI
SSD 2 X Samsung 850 Pro 1TB
HDD 2 X WD RE 4TB
MOBO Asus Rampage V Extreme
PSU Corsair AX 1500i
CASE Corsair 900D
DISPLAY 2 X ROG Swift
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12 REPLIES 12

BenchZowner
Level 7
For what ?
Gaming with a PCI-Express VGA ? None.
Desktop usage ? None.
A few applications ( WinRAR, 7-zip, WinZIP, KGB, SAP, high traffic SQL Server ) ? The best of both worlds, and also depends on the platform ( chipset + CPU )

If you're talking about your system, and your primary usage ( which is gaming most likely with your GTX 580 SLI ) then... get a decent DDR3-1600 memory kit with the capacity of your desire ( anything from 6GB and more is the top you can get for gaming performance ).

Data and proof to back it up ? Sure, go ahead and read my extended testing article

http://www.benchzone.com/page.php?al=gaming_performance_part1

Zka17
Level 16
Regarding the system memory the most important is to have it running stable... a bad memory can really mess up things... - whatever settings you choose, run memtest86+ for at least 4 cycles, if it passes, then most likely you're fine...

If you're in benching, then 2400MHz CL10 is better than 1866MHz CL9... - just be aware that not all systems are the same, and there is no guarantee that you can actually reach those memory speeds... (it's about the chip's lottery)

Arne_Saknussemm
Level 40
There is a formula that can help you in deciding if one kit is faster than the other when the timings are taken into account.

(CAS/frequency) x 2000 gives you a number in nanoseconds for comparing speeds.

Say you see a 1600 kit at 7-8-7-20 and a 1866 kit at 9-10-9-28 which is faster?
Well 7/1600 x 2000 = 8.75 nanoseconds; 9/1866 x 2000 = 9.646 so the 1600 kit actually looks quicker.

If these numbers are close or the same choose the higher frequency it will be more efficient.

Arne, what you calculated there isn't the memory latency? If so, higher latency doesn't mean that your RAM is actually slower?

So, 9.646 ns is actually worse than 8.75 ns... the first takes more time...

Arne Saknussemm wrote:
(CAS/frequency) x 2000 gives you a number in nanoseconds for comparing speeds.

Could you explain this formula?

Looking at the units I see CAS is in clock cycles, frequency is mega clock cycles per second, so the formula yields an answer in micro seconds.
So where does the 2 come from? I'm guessing this is an approximate formula, and the real one uses a second point of data; (CAS+???)/F * 1000 ?

Gorman wrote:
So where does the 2 come from?


DDR. The advertised speeds are double the actual clock cycles so dividing by that number will give you an artificially halved time.

Ah nm, I just check Arne's link and Raja gave the same explanation. Oh well, carry on. 😄
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Arne_Saknussemm
Level 40
Correct!:rolleyes: the latency is the CAS no..... the formula uses latency not calculates it......it lets you know which kit is faster when comparing different speed RAM with different latencies....;) I thought Florre might have been wanting to know that (maybe my mistake).

1866 cas 9.. 9.6462 slow
2400 cas 11.. 9.1666 faster
2400 cas 10.. 8.3332 fastest

Arne Saknussemm wrote:
Correct!:rolleyes: the latency is the CAS no..... the formula uses latency not calculates it......it lets you know which kit is faster when comparing different speed RAM with different latencies....;) I thought Florre might have been wanting to know that (maybe my mistake).

1866 cas 9.. 9.6462 slow
2400 cas 11.. 9.1666 faster
2400 cas 10.. 8.3332 fastest




Thanks for the formula. Its proving to be damn useful!

Thx.
CPU Intel i7 5960X@ 4.5Ghz
RAM Corsair Dominator Platinum 32GB 2400mhz
GPU 2 X EVGA GTX 980 in SLI
SSD 2 X Samsung 850 Pro 1TB
HDD 2 X WD RE 4TB
MOBO Asus Rampage V Extreme
PSU Corsair AX 1500i
CASE Corsair 900D
DISPLAY 2 X ROG Swift

Arne_Saknussemm
Level 40