[SOLVED] Mhz and cas

[MdizzleD]

I'm trying to decide between two sets of ram right now: one is 3600mhz cas 14 and the other is 4000mhz cas 18. Both same brand, but the 4000mhz ram is much cheaper. What is your input when directly comparing these two sets? (Both are Teamgroup t-force xtreem argb).

 

[SamirD]

Faster=better, especially since the 4000 will probably fall back to cas 14 at 3600.

 

[MdizzleD]

Faster=better, especially since the 4000 will probably fall back to cas 14 at 3600.

does it fall back to cas 14 automatically or do I need to change that in the bios/xmp

 

[madmatt30]

Faster=better, especially since the 4000 will probably fall back to cas 14 at 3600.

does it fall back to cas 14 automatically or do I need to change that in the bios/xmp

The 4000 will likely be cas 15/16 at 3600mhz.

I wouldn't sweat that at all personally, if the price difference is really that big then just go for the 4000mhz stuff.

You're not going to notice a perfoemance difference outside of memory benchmarking.

Always a big price tradeoff between ram speeds and latencies, you just have to be sensible about it.

 

[SamirD]

does it fall back to cas 14 automatically or do I need to change that in the bios/xmp

I'm not sure if you'd have to change it in bios because it really depends on the motherboard and the ram's defaults.

 

[MdizzleD]

I'm not sure if you'd have to change it in bios because it really depends on the motherboard and the ram's defaults.

Price isn't a big factor in my decision. I just want to make sure I'm getting the better ram.

 

[madmatt30]

Price isn't a big factor in my decision. I just want to make sure I'm getting the better ram.

Unless you have money burning a hole in your pocket just go with the cheaper of the two.

You are honestly not going to see a performance difference in real life.

What's the actual price difference??

 

[MdizzleD]

Unless you have money burning a hole in your pocket just go with the cheaper of the two.

You are honestly not going to see a performance difference in real life.

What's the actual price difference??

4000 cas 18 is $160 USD and the 3600 cas 14 is $210 USD

 

[MdizzleD]

4000 cas 18 is $160 USD and the 3600 cas 14 is $210 USD

4000 cas 18 is $160 USD and the 3600 cas 14 is $210 USD

Your thoughts?

 

[madmatt30]

Your thoughts?

With a 30% premium I'd Personally go with the cheaper 4000mhz, like I said its a tradeoff, $20 may be worth it just maybe, $50 definitely isn't.

What is the rest of your setup??

The 3600 is samsung b-die, the 4000 is hynix-a.

While on ryzen gen 1 and 2 that may make a difference, on Intel or ryzen 3 (5*** series) timings generally make very little difference.

Enable xmp with the 4000 and drop the clock to 3600 and it'll likely run cas 16, the difference between the 3600 cas 14 and the 4000 running at 3y00 cas 16 is probably going to be about 1-2% max.

You're not going to notice that difference at all

The 3600 is better ram, just not $50 better imo.

 

[mamasan2000]

In general, to calculate CL between 2 different speed sticks, for every 200 Mhz, you subtract/add 1 to CL. Depending which way you count. So 4000 Mhz CL 18 -> 3800 Mhz CL 17 -> 3600 Mhz CL 16. You could just reverse the arrow in my example and it would be generally true too, provided the sticks can run 4000 Mhz, which isn't a guarantee. In other words, 3600 Mhz CL 16 sticks are not guaranteed to work at 4000 Mhz CL 18. Next step down would be 3800 Mhz CL 17. See the pattern?

A CAS Latency difference of one wont make a huge difference. And CL generally scales with voltage. The higher the voltage, the lower you can go, up to a point. You will hit a wall here too.
But things like tRFC can make a big difference. I was reading some documentation from Micron or Hynix and they calculated the RAM refreshing taking up between 4.5%-6.7% of ALL the cycles. tRFC = Cycles before RAM refreshes. Samsung B-die is notorious for having a very low tRFC, half in fact of every other memory. So that should be a solid gain. There was a graph of someone testing each timing and how it affected games. I want to remember stuff like tRTP had a couple percentages in perf improvement. Wish I could find it again. In other words, it's not only primaries that will gain you performance, look at secondary and tertiary timings too.

 

[MdizzleD]

With a 30% premium I'd Personally go with the cheaper 4000mhz, like I said its a tradeoff, $20 may be worth it just maybe, $50 definitely isn't.

What is the rest of your setup??

The 3600 is samsung b-die, the 4000 is hynix-a.

While on ryzen gen 1 and 2 that may make a difference, on Intel or ryzen 3 (5*** series) timings generally make very little difference.

Enable xmp with the 4000 and drop the clock to 3600 and it'll likely run cas 16, the difference between the 3600 cas 14 and the 4000 running at 3y00 cas 16 is probably going to be about 1-2% max.

You're not going to notice that difference at all

The 3600 is better ram, just not $50 better imo.

Well, I'm building a PC right now and don't have all my parts yet. I will list an idea of what I plan on building here shortly.

 

[MdizzleD]

With a 30% premium I'd Personally go with the cheaper 4000mhz, like I said its a tradeoff, $20 may be worth it just maybe, $50 definitely isn't.

What is the rest of your setup??

The 3600 is samsung b-die, the 4000 is hynix-a.

While on ryzen gen 1 and 2 that may make a difference, on Intel or ryzen 3 (5*** series) timings generally make very little difference.

Enable xmp with the 4000 and drop the clock to 3600 and it'll likely run cas 16, the difference between the 3600 cas 14 and the 4000 running at 3y00 cas 16 is probably going to be about 1-2% max.

You're not going to notice that difference at all

The 3600 is better ram, just not $50 better imo.

madmatt30-here is what I'm thinking:
CPU-5900x
GPU-3090 fe
Mobo-ASRock X570 PG Velocita or X570 Taichi
RAM-Teamgroup 4000 cl18 or 3600 cl14
SSD-Samsung Pro 980

 

[MdizzleD]

Any other thoughts?

 

[JWNoctis]

One thing that no one seemed to have mentioned so far, is Infinity Fabric/memory clock desync if you are getting a Ryzen.

This may result in said 4000MHz module actually running better at 3600, as few non-APU Ryzens seemed to run stable much abouve 1800MHz FCLK, or so I heard.

Might be useful reading up on that a bit, if you do.

 

[Endre]

I'm trying to decide between two sets of ram right now: one is 3600mhz cas 14 and the other is 4000mhz cas 18. Both same brand, but the 4000mhz ram is much cheaper. What is your input when directly comparing these two sets? (Both are Teamgroup t-force xtreem argb).

The difference between those two is defined by responsiveness, which is being measured in nanoseconds (lower is better).

DDR4-3600 CL14 = 7.77ns (better)
DDR4-4000 CL18 = 9ns (worse)

Also, please keep in mind that DDR4-4000 is not being supported by most motherboards (sometimes even if the specs sheet say it does).

 

[MdizzleD]

The difference between those two is defined by responsiveness, which is being measured in nanoseconds (lower is better).

DDR4-3600 CL14 = 7.77ns (better)
DDR4-4000 CL18 = 9ns (worse)

Also, please keep in mind that DDR4-4000 is not being supported by most motherboards (sometimes even if the specs sheet say it does).

How could you find out if a motherboard is able to handle it legitimately?

 

[Endre]

How could you find out if a motherboard is able to handle it legitimately?

The vendor will have that specified in the manual of the motherboard.
But you should take those informations with “a grain of salt”.

XMP is a “safe” overclock, but still: it’s an overclock. It hasn’t been approved by JEDEC or Intel/AMD!
On DDR4, any voltage above 1.2V is an overclock!

CONCLUSION:
You can’t know for sure if it will work, usually it does if the vendor says so.
Sometimes it does work for a few months, then later, it falls at JEDEC speeds: 2133 or 2400 @1.2V.

ADVICE:
Make sure you have decent cooling solutions. Don’t cheap out!
Also, lower DDR4 speeds like: 2666, 2933, 3200, 3466 are a safer bet that they’ll work.

 

[mamasan2000]

One thing that no one seemed to have mentioned so far, is Infinity Fabric/memory clock desync if you are getting a Ryzen.

This may result in said 4000MHz module actually running better at 3600, as few non-APU Ryzens seemed to run stable much abouve 1800MHz FCLK, or so I heard.

Might be useful reading up on that a bit, if you do.

That is pretty much a given. Quite rare to have Fclock run at 2000 Mhz. So I wouldn't count on running 4000 Mhz RAM at 4000 Mhz. 1900 should work quite often. It's down to the CPU and IMC.
I've read something about newer AGESAs also possibly not allowing 2000 Fclock. But on that I'm not sure at all.
1900 Fclock is the best my 5600X can do. Any higher and I get tons of WHEA error 19. Bus error. Not good.

I'm guessing the kits are 16 gig. 3600 Mhz @ CL14 is 99% for sure B-die. Best RAM you can get. But also twice the price compared to 'normal' RAM. Something like CL16 or 18.
Wasn't worth it for me, I went with 32 gigs instead for 200 dollars.

 

[MdizzleD]

The vendor will have that specified in the manual of the motherboard.
But you should take those informations with “a grain of salt”.

XMP is a “safe” overclock, but still: it’s an overclock. It hasn’t been approved by JEDEC or Intel/AMD!
On DDR4, any voltage above 1.2V is an overclock!

CONCLUSION:
You can’t know for sure if it will work, usually it does if the vendor says so.
Sometimes it does work for a few months, then later, it falls at JEDEC speeds: 2133 or 2400 @1.2V.

ADVICE:
Make sure you have decent cooling solutions. Don’t cheap out!
Also, lower DDR4 speeds like: 2666, 2933, 3200, 3466 are a safer bet that they’ll work.

So what you're saying is that the 3600 is better because of the lower latency and that the slower DRAM speed is more stable while the 4000(is opposite) but COULD be a better performer when ran at the lower voltage?

 

[Ralston18]

What make and model motherboard? Version?

Go to the motherboard manufacturer's website.

Find the applicable motherboard User Guide/Manual for the motherboard and check all the supported components.

Read all of the fine print, notes, warnings, etc.. For example, there may be a requirement that the first physically installed RAM module be placed in a specific RAM slot., Be sure that you get RAM kits with matched modules for dual channel use.

Likely the User Guide Manual will refer you back to the motherboard manufacturer's website for more up to date information.

Do that and while you are there peruse any applicable Forums and FAQ's. Look for what is said and what is not said.

Details matter.

 

[MdizzleD]

What make and model motherboard? Version?

Go to the motherboard manufacturer's website.

Find the applicable motherboard User Guide/Manual for the motherboard and check all the supported components.

Read all of the fine print, notes, warnings, etc.. For example, there may be a requirement that the first physically installed RAM module be placed in a specific RAM slot., Be sure that you get RAM kits with matched modules for dual channel use.

Likely the User Guide Manual will refer you back to the motherboard manufacturer's website for more up to date information.

Do that and while you are there peruse any applicable Forums and FAQ's. Look for what is said and what is not said.

Details matter.

either: Mobo-ASRock X570 PG Velocita or X570 Taichi

 

[Ralston18]

For the Asrock:

https://download.asrock.com/Manual/X570 PG Velocita.pdf

Reference Section 2.3 beginning on physical numbered Page 24.

For example:

"We suggest that you install the memory modules on DDR4_A2 and DDR4_B2 first for better DRAM compatibility on 2 DIMMs configuration. "

[Do verify that I found the correct User Manual.]

 

[MdizzleD]

For the Asrock:

https://download.asrock.com/Manual/X570 PG Velocita.pdf

Reference Section 2.3 beginning on physical numbered Page 24.

For example:

"We suggest that you install the memory modules on DDR4_A2 and DDR4_B2 first for better DRAM compatibility on 2 DIMMs configuration. "

[Do verify that I found the correct User Manual.]

OK. I understand the DIIMM placement, but it only shows up to 3200Mhz even thought the specs on Newegg say well over that. Is that because it is only verified up to 3200Mhz but not the overclocking speeds mentioned on Newegg? Also, SR & DR?

 

[Ralston18]

The guiding documents are the manufacturer's motherboard specs, the User Manual, and whatever updates may be available via the motherboard manufacturer's website. The QVL's (Qualified Vendor's List) in particular.

You can do some cross checking via the various RAM module manufacturer's to determine if there is a consensus or differing information with respect to what RAM modules will work in any given motherboard and in what configurations.

I would not rely on any seller's ads or specs with regards to what will and will not work. Those ads are often just quick cut and paste products from other earlier ads and all too likely contain errors of omission or commission. Both text and images. Even obvious mistakes are sometimes left....

"Caveat Emptor".