Ram speed, Cas Latency and timing?

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MKV123

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Jul 20, 2017
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Bulding a high end pc but having a hard time understanding what ram to go for?

The ram i was considering has these specifications
speed: 4266| Cas: 19| Timing 19-19-19-39

Another example
speed 2666| cas 15| timing 15-15-15-35


The cas and timing increase with higher ramspeed and decrease with lower
Would it be better in this case to go with higher speed or lower speed ram?
 
Solution
R_1
THE RULE:
as the speeds increase so must the timings. plain old DDR had timings in the low single digits, but ran at 400Mhz.
the timings are measured in clock cycles, as the speeds increase each single cycle is shorter, enough of the shorter cycles means you can get a higher timing number. although the timings increase the measuring stick is getting smaller (shorter clock cycles) which leads to higher timings and faster absolute speeds.

if you are getting 3200Mhz ram try to get the ram with the lowest timings in that class.
you cannot compare the timings like 4266 and 2666 because the measuring sticks differ, but the faster RAM will be faster in spite of and because of the higher timings.

consider each speed of RAM its own class and...
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R_1

R_1

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Sep 8, 2015
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THE RULE:
as the speeds increase so must the timings. plain old DDR had timings in the low single digits, but ran at 400Mhz.
the timings are measured in clock cycles, as the speeds increase each single cycle is shorter, enough of the shorter cycles means you can get a higher timing number. although the timings increase the measuring stick is getting smaller (shorter clock cycles) which leads to higher timings and faster absolute speeds.

if you are getting 3200Mhz ram try to get the ram with the lowest timings in that class.
you cannot compare the timings like 4266 and 2666 because the measuring sticks differ, but the faster RAM will be faster in spite of and because of the higher timings.

consider each speed of RAM its own class and get the lowest available timing in the speed you need.
The memory controller is in the CPU, do not go beyond what it can support
 
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Solution
photonboy

photonboy

Titan
Jun 20, 2006
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85,015
Hi,
The MAIN CONCERN is what CPU you are using.

Most modern AMD and Intel CPU's see very little benefit beyond 3200MHz Dual Channel DDR4 regardless of the latency values.

Also, if this is a motherboard with QUAD CHANNEL support you can get away with lower frequency sticks of memory though again it also depends on what CPU you are using.

*If in doubt for something like an i7-8700K I would stick with 3200MHz (i.e. 2x8GB) or slightly higher but I wouldn't waste money going above 4000MHz.

**You can also DAMAGE THE CPU by having memory with higher voltage. They are only rated up to a specific voltage after which you are more and more likely to kill your CPU as the voltage increases beyond the recommended amount.
 
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