Confused about cas latency

[PeggersXtreme]

hi,

 

So I posted a few days ago about 3000mhz ram vs 2666mhz ram but didn't realise the difference in cas latency one is cas 16 the other is cas 15 what do these mean?

I've not really ever dived into much detail of ram.

[Stardar1]

1 minute ago, PeggersXtreme said:

hi,

 

So I posted a few days ago about 3000mhz ram vs 2666mhz ram but didn't realise the difference in cas latency one is cas 16 the other is cas 15 what do these mean?

I've not really ever dived into much detail of ram.

the short answer is that a lower CAS is better. 

 

for the long answer, visit this link:

https://en.wikipedia.org/wiki/CAS_latency

[PeggersXtreme]

2 minutes ago, Stardar1 said:

the short answer is that a lower CAS is better. 

 

for the long answer, visit this link:

https://en.wikipedia.org/wiki/CAS_latency

Oh ok I get that it's latency but isn't the Crucial Ballistix Elite range meant to be their flagship ram and the tactical meant to be their second in the line up I don't get why the elite is cas 16 and tactical is cas 15 if the elite is meant to be better if you get what I mean

[Stardar1]

Just now, PeggersXtreme said:

Oh ok I get that it's latency but isn't the Crucial Ballistix Elite range meant to be their flagship ram and the tactical meant to be their second in the line up I don't get why the elite is cas 16 and tactical is cas 15 if the elite is meant to be better if you get what I mean

Generally speaking, as one increases the frequency (clock speed) of RAM, they increase the CAS as well. 

 

it's not that huge a deal, and you probably won't notice a difference

[PeggersXtreme]

1 minute ago, Stardar1 said:

Generally speaking, as one increases the frequency (clock speed) of RAM, they increase the CAS as well. 

 

it's not that huge a deal, and you probably won't notice a difference

oh right the tactical ram is 3000mhz cas 15 and the ballistix elite that I ordered is 2666mhz cas 16

[Mira Yurizaki]

Also keep in mind CAS latency is measured in clock cycles. So lower CAS latency is only better for RAM of the same speed, otherwise you have to do some math to figure out which one is truly better.

 

For example, CAS latency on DDR-400 is usually 4 or 5, while today's DDR4-2166 gets up to 15. Is DDR4-2166 worse than DDR-400 for CAS latency? No, because the DDR-400 module needs 12.5ns to do that step, whereas DDR4-2166 needs 6.9 or so ns.

[Sakkura]

5 minutes ago, PeggersXtreme said:

Oh ok I get that it's latency but isn't the Crucial Ballistix Elite range meant to be their flagship ram and the tactical meant to be their second in the line up I don't get why the elite is cas 16 and tactical is cas 15 if the elite is meant to be better if you get what I mean

The CAS latency is measured in clock cycles, which get shorter at higher clocks. DDR4-3000 CL16 has lower latency than DDR4-2666 CL15.

 

Edit: Oh the CL numbers are even the other way around. Then the latency on the faster clocked kit is WAY lower.

[PeggersXtreme]

2 minutes ago, Sakkura said:

The CAS latency is measured in clock cycles, which get shorter at higher clocks. DDR4-3000 CL16 has lower latency than DDR4-2666 CL15.

So the Tactical is actually the better ram the elite just looks better on paper because of it's little features like temp probes which I thought all ram modules had some type of temperature probe maybe i'm wrong but hardware monitor has always given me a ram temp

[PeggersXtreme]

13 minutes ago, M.Yurizaki said:

Also keep in mind CAS latency is measured in clock cycles. So lower CAS latency is only better for RAM of the same speed, otherwise you have to do some math to figure out which one is truly better.

 

For example, CAS latency on DDR-400 is usually 4 or 5, while today's DDR4-2166 gets up to 15. Is DDR4-2166 worse than DDR-400 for CAS latency? No, because the DDR-400 module needs 12.5ns to do that step, whereas DDR4-2166 needs 6.9 or so ns.

May actually return the ballistix elite when they arrive in that case and get the tacticals for the extra £15 they are cas 15 3000mhz and the ones I ordered are 2666mhz at cas 16

[Sakkura]

12 minutes ago, PeggersXtreme said:

So the Tactical is actually the better ram the elite just looks better on paper because of it's little features like temp probes which I thought all ram modules had some type of temperature probe maybe i'm wrong but hardware monitor has always given me a ram temp

Well, RAM models usually come in a variety of speeds. So maybe you're comparing a slower member of one family to a faster member of another.

[PeggersXtreme]

Just now, Sakkura said:

Well, RAM models usually come in a variety of speeds. So maybe you're comparing a slower member of one family to a faster member of another.

maybe that is the case I will probably return the ram when it arrives and get the Cas15 stuff I know the difference will be minimal but I was using corsair cas 15 ram before and don't want to take a downgrade the only reason I went with crucial this time was I used it in all my builds when DDR3 was the norm and never had issues like I have had with corsair ram it causes post issues for some reason yet when I do a mem test all stick are good apparently