CAS latency vs PC speed

[TheLostViking]

Generally speaking, I've built all my computers to have the lowest CAS latency RAM. In the days of DDR3 1866-2400 this wasn't really that big of a deal, just grab some CAS 12 or lower and slap those bad boys in. However, now we've got DDR4 approaching the 5000 mark, but with CAS latency of 15 or greater.

 

Am I just being a dinosaur when I'd rather drop in a DDR4 2400 with a CAS latency of 10 versus a DDR4 4800 with a CAS latency of 18 or is the greater PC speed able to make up for the difference in latency after a certain GB threshold/performance point?

 

I only ask because my pride has taken a hit a few times on certain subreddits when my builds get criticized for not featuring higher speed RAM despite them having greater latency and I'm admittedly not as knowledgeable about the topic as I'd like to be. 

[Fasauceome]

The cas number, be it 12, 10, 15, etc., is a multiplier. The actual real world latency is also dependent on the frequency. A cas 15 kit of DDR4 3200 has lower latency than a cas 10 kit of DDR3 1600

[mariushm]

Latency used to matter more, it's  less important now as cpus have bigger  caches (ex up to 72MB on Ryzen)

Latency is more important to apps. that deal often with random and  small chunks of  data (databases for  ex) games and most apps don't care.

Intel cpus care less about ram frequency.

Ryzen does,higher frequency (up to a  point) improves performance, due  to internal design (infinity fabric which connects  everything  inside  like a data highway  runs at same speed as ram)  

[.Apex.]

Youre misinformed about CAS latency, as @fasauceome said, the real latency also depends on frequency, it's kind of a balance, overall most kits have similar latencies, but the advantage of higher frequency kits is the increased bandwidth

 

Heres a simple latency calculator 

https://notkyon.moe/ram-latency.htm

[Alex Atkin UK]

22 minutes ago, mariushm said:

Latency used to matter more, it's  less important now as cpus have bigger  caches (ex up to 72MB on Ryzen)

Latency is more important to apps. that deal often with random and  small chunks of  data (databases for  ex) games and most apps don't care.

Intel cpus care less about ram frequency.

Ryzen does,higher frequency (up to a  point) improves performance, due  to internal design (infinity fabric which connects  everything  inside  like a data highway  runs at same speed as ram)  

Intel caring less is not quite as clear cut as people make out.

 

I upgraded from 16GB 2400Mhz to 32GB 3200Mhz and it allowed me to go from 50-60fps on Assassins Creed Odyssey at 4K 70% scaling on an 8600K, to a solid 60fps.  So yes, RAM speed DOES make a notable difference, even on Intel.  It just doesn't make quite as big a difference as on Ryzen.

[TheLostViking]

18 hours ago, _Syn_ said:

Youre misinformed about CAS latency, as @fasauceome said, the real latency also depends on frequency, it's kind of a balance, overall most kits have similar latencies, but the advantage of higher frequency kits is the increased bandwidth

 

Heres a simple latency calculator 

https://notkyon.moe/ram-latency.htm

Added to favorites bar. I feel like a huge idiot for not searching "RAM latency calculator" sooner.