How do i read memory latency?

[heckboi]

I'm shopping around a good 32gig kit of memory to go with my 7800x3d. I was told to look for 6000mhz c32/30 kits. I'm not really sure how to read memory latency. For example, in a c30 kit, should i look for kits with numbers as close to "30" as possible?

 

[YoungBlade]

The memory timings give you the speed in clock cycles. So CL 30 means that the CAS Latency is 30 clock cycles. The actual speed of DDR5-6000 is 3000MHz (this is a case where the difference between speed and frequency actually matters).

 

3000 MHz = 3,000,000,000 Hz = 3,000,000,000 times per second

 

3,000,000,000 times per second / 30 = 100,000,000 times per second

 

100,000,000 times per second = 1 time / 100,000,000 times per second = 0.00000 001 seconds = 10 nanoseconds

 

Thus, the actual CAS Latency in seconds is 10 nanoseconds.

 

In general, for RAM timings, lower number = better, but this is relative to the clockspeed. DDR4-3200 CL16 and DDR5-6400 CL32 and DDR5-6000 CL30 and DDR3-1600 CL8 all actually have identical CAS Latency in terms of actual nanoseconds, which is ultimately what matters.

[Eigenvektor]

7 minutes ago, heckboi said:

For example, in a c30 kit, should i look for kits with numbers as close to "30" as possible?

When it comes to latency, lower means better. The reason you're told to look for kits with CL 30 is because they're generally good in terms of price to performance. If you can find a kit with a lower number that is better, but most likely it'll be too expensive for the additional performance you get.

[GuiltySpark_]

10 minutes ago, heckboi said:

I'm shopping around a good 32gig kit of memory to go with my 7800x3d. I was told to look for 6000mhz c32/30 kits. I'm not really sure how to read memory latency. For example, in a c30 kit, should i look for kits with numbers as close to "30" as possible?

 

What region of the world are you from? Good, well priced kits are usually easy to find.

[YoungBlade]

Just now, Eigenvektor said:

When it comes to latency, lower means better. The reason you're told to look for kits with CL 30 is because they're generally good in terms of price to performance. If you can find a kit with a lower number that is better, but most likely it'll be too expensive for the additional performance you get.

Yes, but remember that this is only true for a given clockspeed.

 

DDR5-5200 CL28 is actually slower in terms of latency than DDR5-6000 CL30 despite having a lower CL on the box.

[Eigenvektor]

1 minute ago, YoungBlade said:

Yes, but remember that this is only true for a given clockspeed.

 

DDR5-5200 CL28 is actually slower in terms of latency than DDR5-6000 CL30 despite having a lower CL on the box.

Yes, absolutely. I wanted to keep it simply, plus you'd covered that part already

[heckboi]

Whats the difference between SPD latency and tested latency?