Question What's more important in RAM specs, CL or speed (MHz) ?

[MikeW20]

Hi, I was thinking of upgrading my current RAM. So, I was thinking if I should get 3600MHz 2x16gb RAM CL 18 or 3200MHz 2x16gb RAM CL16. Will there be huge difference between the two?

 

[SkyNetRising]

I was thinking if I should get 3600MHz 2x16gb RAM CL 18 or 3200MHz 2x16gb RAM CL16.
Will there be huge difference between the two?

They are the same. Basically no difference.
Higher frequency increases performance. Higher latency decreases performance.
Increased frequency of 3600mhz gets balanced out by increased latency.
You can compare performance this way:
3600/18 = 3200/16

 

[MikeW20]

Oh ok. Thanks for the answer. The 3600MHz CL18 is slightly more expensive, but since there's not really that much difference, I will probably go with 3200MHz CL 16.

 

[BFG-9000]

It depends on your platform.

They may have the same latency but the 3600MHz has more bandwidth. That could be useful if you are running the IGP which really isn't sensitive to latency but could use all the bandwidth you can give it. There's really no difference if you are using a GPU.

Running faster than 3600 on Ryzen drops the Infinity Fabric from 1:1 for a considerable latency penalty

 

[PEnns]

Running faster than 3600 on Ryzen drops the Infinity Fabric from 1:1 for a considerable latency penalty

Does this apply to both DDR4 AND DDR5??

 

[geofelt]

What are the parts you now have?
Why are you thinking of changing?
Capacity or performance? or??

Intel cpu will not likely significantly benefit from faster ram.
Ryzen is very dependent on ram speed but is finicky about compatibility.

To answer your question, no, there is not a huge difference between the two.
There are some ram sensitive apps where it may be relevant.
If you take the ram speed and divide by the cas, you will get the same figure of merit of about 200.

Think of ram as a drag race where the objective is to fetch some data in the least possible time.
One car has good acceleration to get up to speed, and the other has slower acceleration, but a higher top end speed. Who gets to the end in the shortest time??

 

[BFG-9000]

Does this apply to both DDR4 AND DDR5??

Yes, because the limitation is how fast the Infinity Fabric is stable at until it has to drop to 1:2 to remain stable.
All Ryzens have their "sweet spot" and this changes over generations as the memory controller improves. For example the 3000 series appears to be best at DDR4-3733 but look at that 3200 with tight timings:

While the 5000 series is best at DDR4-4000 but 4133 is nearly as good if that's a typo and it's 55.3ns or 56.3ns:

The 7000 series is supposed to be best at DDR5-6000.

But the OP hasn't let us know what platform they have, and it may well be Intel for all we know.

 

[MikeW20]

Answering your questions, I currently have Intel Core i5-11400F but I am definitely going to upgrade to i5-13600K. I am thinking of changing RAM mainly due to capacity to 32GB from 16GB i have right now, but better performance won’t hurt.

 

[geofelt]

Do you really need more than 16gb now?
If you primarily do one thing at a time, like gaming, 16gb should be ok.
Memory usage via task manager will be misleading.
Windows keeps unused code in ram in anticipation of quick reuse.
To see if lack of ram is now impacting you, look at task manager/resource monitor/memory tab.
Check the hard fault page rate which is an indicator of ram shortage.
With sufficient ram, the rate should be zero.
A hard fault happens when windows needs to steal an active ram page.
That is not good.
If you will be streaming or other multitasking while gaming on the 13600K, then possibly more ram will be useful.
I think If in doubt, wait for the new processor and see how you do.
It is easy to upgrade ram later.

As to 3600/18 or 3200/16, I think I would pick the 3600/18 option.
Of course, if budget is not important, you can pay double and buy 3600/16.

 

[MikeW20]

Well, I mainly use my PC for work and gaming. I work with 2 or more virtual machines during the day at the same time and sometimes, I feel that my PC just can’t handle multiple VMs. That’s why I wanted to upgrade the RAM to at least 32GB.

 

[geofelt]

Well, I mainly use my PC for work and gaming. I work with 2 or more virtual machines during the day at the same time and sometimes, I feel that my PC just can’t handle multiple VMs. That’s why I wanted to upgrade the RAM to at least 32GB.

That sounds to me like a good reason for 32gb.