Jump to content
Search In
  • More options...
Find results that contain...
Find results in...

ram speed vs cas latency

Hypothetical question, I don't actually plan on buying any ram in the near future... but I was wondering as far as gaming goes what would be the best kit out of these three? 

 

Corsair Vengeance 

3000 cl 15

3200 cl 16

3600 cl 18

 

In the past (DDR3 days...) once you got up to a certain speed (about 1600 ish), speed didn't really matter anymore and a lower cas latency was more important... is that still true? Or did something change...

 

Screenshot_20201126-131647_Chrome.jpg

No Excuses, Play Like A Champion!!!  

Link to post
Share on other sites

CL15 @ 3000 = 10 nanoseconds latency

CL16 @ 3200 = 10 nanoseconds latency

CL18 @ 3600 = 10 nanoseconds latency

 

So the absolute latency is the same, since that is a function of the CL number and the frequency.

 

Remember to quote or @mention others, so they are notified of your reply

Link to post
Share on other sites
1 minute ago, Eigenvektor said:

CL15 @ 3000 = 10 nanoseconds latency

CL16 @ 3200 = 10 nanoseconds latency

CL18 @ 3600 = 10 nanoseconds latency

 

So the absolute latency is the same, since that is a function of the CL number and the frequency.

 

latency is the same for all, in which case the higher frequency of the 3600 gives it an advantage. that's if the cpu can actually run the ram at 3600.

Link to post
Share on other sites
Just now, boggy77 said:

latency is the same for all, in which case the higher frequency of the 3600 gives it an advantage. that's if the cpu can actually run the ram at 3600.

Agreed. Latency being the same means frequency (=speed) wins.

 

To give a bit more info: The CAS Latency number is expressed in number of clock cycles. Higher frequency = clock cycle is faster = absolute latency is lower.

Remember to quote or @mention others, so they are notified of your reply

Link to post
Share on other sites
15 minutes ago, Eigenvektor said:

Agreed. Latency being the same means frequency (=speed) wins.

 

To give a bit more info: The CAS Latency number is expressed in number of clock cycles. Higher frequency = clock cycle is faster = absolute latency is lower.

@OP For completeness I will point out that the real clock frequency of the ram is half of what the effective clock is. So 3600MHz ram is actually running at 1800MHz but because it is double data rate so you get 2 bits per clock cycle so double your effective clock.

 

So to calculate CAS latency you would use the real clock and not the effective clock.

CPU: Intel i7 - 5820k @ 4.5GHz, Cooler: Corsair H80i, Motherboard: MSI X99S Gaming 7, RAM: Corsair Vengeance LPX 32GB DDR4 2666MHz CL16,

GPU: ASUS GTX 980 Strix, Case: Corsair 900D, PSU: Corsair AX860i 860W, Keyboard: Logitech G19, Mouse: Corsair M95, Storage: Intel 730 Series 480GB SSD, WD 1.5TB Black

Display: BenQ XL2730Z 2560x1440 144Hz

Link to post
Share on other sites

CAS latency is only one of many timings though, and the large array of others also have some influence in overall results.

 

Still, depends on the software being run, some scale better with overall latency, some scale better with overall bandwidth. I'm not up to speed on what modern games do when it comes to that behaviour. Differences are minor and it isn't going to make or break a system.

Desktop Gaming system: Asrock Z370 Pro4, i7-8086k, Noctua D15, Corsair Vengeance Pro RGB 3200 4x16GB, Gigabyte 2070, NZXT E850 PSU, Cooler Master MasterBox 5, Optane 900p 280GB, Crucial MX200 1TB, Sandisk 960GB, Acer Predator XB241YU 1440p144 G-sync
TV Gaming system: Gigabyte Z490 Elite AC, i5-10600k, Noctua D15, Kingston HyperX RGB 4000@3600 2x8GB, EVGA 2080Ti Black, EVGA 850W, Corsair 230T, Crucial P1 1TB + MX500 1TB, LG OLED55B9PLA 4k120 G-Sync Compatible
Streaming system: Asus X299 TUF mark 2, i9-7920X, Noctua D15, Corsair Vengeance LPX RGB 3000 8x8GB, Asus Strix 1080Ti, Corsair HX1000i, GameMax Abyss, Samsung 970 Evo 500GB, Crucial BX500 1TB, BenQ XL2411 1080p144 + HP LP2475w 1200p60
Former Main system: Asus Maximus VIII Hero, i7-6700k, Noctua D14, G.Skill Ripjaws V 3200 2x8GB, Gigabyte GTX 1650, Corsair HX750i, In Win 303 NVIDIA, Samsung SM951 512GB, WD Blue 1TB, Acer RT280k 4k60 FreeSync [link]
Gaming laptop: Asus FX503VD, i5-7300HQ, DDR4 2133 2x8GB, GTX 1050, Sandisk 256GB + 480GB SSD [link]


 

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×