DDR4 for Zen 3 build - Mhz vs CAS latency?

Blade-Runner

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I am starting to look into components for my first new build in over 8 years and am currently stuck on which RAM modules to go with.

I vaguely remember RAM latency being important, but haven't been able to find a quick and easy answer as to whether that is still the case with the latest CPUs and motherboard chipsets.

The toss up is between the Corsair Vengeance RGB PRO 32GB (2x16GB) DDR4 3600 (PC4-28800) C18 and CORSAIR DOMINATOR PLATINUM RGB 32GB (2x16GB) DDR4 3200 (PC4-25600) C16.

https://www.amazon.com.au/CORSAIR-V...rsair+32gb+ddr4+3600mhz&qid=1602390047&sr=8-3

https://www.amazon.com.au/gp/product/B07N3LDKR1/ref=ox_sc_act_title_1?smid=ANEGB3WVEVKZB&psc=1

Does lower latency trump higher mhz?
 
It...can. But there are a lot of factors regarding it. I believe, and I may be wrong, that cas 16 DDR4 -3200 performed on par with CAS18 DDR4-3600 in Zen 2.

We won’t know for sure how Zen 3 behaves until someone tests it though.
 
IF you are really into memory overclocking, there are a lot of motherboards/CPU's that can hit 3800mhz, and have very low timings and latency. Hopefully that goes over to Zen 3, and hopefully it is easier to overclock the memory.

Right now I am running 3800mhz CL14 memory, and its working like a charm. I havent really fine tuned the memory settings yet, but I really do plan too once Zen 3 comes out.
 
First, I'd avoid Corsair like the plague. The ram you picked is rather mediocre. 3600mhz at C18 is some slow arse stuff, as is 3200mhz at C16. These are most definitely not Samsung IC, probably Micron. When it comes to Ryzen lower latency is generally best. Even better is higher speed with low latency.

What are your goals? Are going to try to run the IMC at max speed? The rumor mills points to the new chips doing 2000mhz on the IMC. And you're gonna need real Samsung ICs to get there. The Patriot Viper memory that has been on sale for 130 at Amazon in 2x8GB 4400/C19 are decent and cheap. Now if you are set on 16GB sticks... you're gonna have to research that. I dunno what sticks offhand that will run those speeds at that density.

https://www.amazon.com/gp/product/B07KXLFDL6
 
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IF you are really into memory overclocking, there are a lot of motherboards/CPU's that can hit 3800mhz, and have very low timings and latency. Hopefully that goes over to Zen 3, and hopefully it is easier to overclock the memory.

Right now I am running 3800mhz CL14 memory, and its working like a charm. I havent really fine tuned the memory settings yet, but I really do plan too once Zen 3 comes out.

I used to spend a bit of time overclocking memory, not so much these days but I imagine I will try to eek out some additional free performance from the CPU and memory if I can.

Those are some nice memory modules...didn't know they existed. Are crazy expensive though and not widely available in my region.
 
First, I'd avoid Corsair like the plague. The ram you picked is rather mediocre. 3600mhz at C18 is some slow arse stuff, as is 3200mhz at C16. These are most definitely not Samsung IC, probably Micron. When it comes to Ryzen lower latency is generally best. Even better is higher speed with low latency.

What are your goals? Are going to try to run the IMC at max speed? The rumor mills points to the new chips doing 2000mhz on the IMC. And you're gonna need real Samsung ICs to get there. The Patriot Viper memory that has been on sale for 130 at Amazon in 2x8GB 4400/C19 are decent and cheap. Now if you are set on 16GB sticks... you're gonna have to research that. I dunno what sticks offhand that will run those speeds at that density.

Thanks for the advice. First time I have seen it suggested to avoid Corsair, have used them for years over several builds without issue.
 
Thanks for the advice. First time I have seen it suggested to avoid Corsair, have used them for years over several builds without issue.

They've gone to shit these past couple years. They label these kits Pro and Platinum and price em like they are, but the IC used are crap.

For the cost of the kits you linked you could buy b-dies in that density with tight matched timings and for LESS.

https://www.newegg.com/g-skill-32gb-288-pin-ddr4-sdram/p/N82E16820232860
 
I used to spend a bit of time overclocking memory, not so much these days but I imagine I will try to eek out some additional free performance from the CPU and memory if I can.

Those are some nice memory modules...didn't know they existed. Are crazy expensive though and not widely available in my region.
O yeah no joke they are expensive, but I can tell you they do work at the rated speed (they literally are made for Ryzen). I got a feeling they will be in demand once Ryzen 3 comes out. Really hoping we will be able to push the memory and Infinity Fabric speeds even higher.
 
I literally just pulled up those G.Skill modules on Amazon....am definitely leaning towards them.

Those are about the best you can get before moving to super high binned kits using the same IC, just very highly binned. I'm using that kit in a Threadripper build. Amazingly I was able to run 3400mhz on the ram at C14 at 128gb density. That ram can run 3800mhz cas 14 as well you just have to jack the voltage way up there.

https://hardforum.com/threads/build-3970x-dual-2080ti-8tb-m-2-raid-render-monster.1990145/
 
Those are about the best you can get before moving to super high binned kits using the same IC, just very highly binned. I'm using that kit in a Threadripper build. Amazingly I was able to run 3400mhz on the ram at C14 at 128gb density. That ram can run 3800mhz cas 14 as well you just have to jack the voltage way up there.

https://hardforum.com/threads/build-3970x-dual-2080ti-8tb-m-2-raid-render-monster.1990145/

Bad ass system! May I ask how are those Sabrent NVMe drives? Never heard of the brand before. And which drives have you paired the AORUS Gen4 SSD AIC Adapter with - the 4tbs?
 
Thanks for the advice. First time I have seen it suggested to avoid Corsair, have used them for years over several builds without issue.
Corsair has amazing warranty support and customer service. Would your average person tell the difference between C14 and C16 3200 ram? Google the results and you'll see, the answer is no. Not even close. If you want the extra few fps, then go for it. If you want to overclock to 3600 c16 or so, get the 3200 c14. If you are not going to overclock, buy whatever you want and set xmp and forget it.

You will not find many Corsair haters. Corsair has been around a long time and is legendary with their customer service.
 
It's not that corsair is bad, it's just that it's hit or miss on what you end up with as they use the same model with different IC chips and you won't know which revision you end up with when ordering. G. Skill has been much more consistent with getting what you expect. One (non official and not 100%) way to know if you're getting decent IC's is to make sure the major numbers are the same. For example, if you have 3600 16-19-19 or you find 3600 16-16-16, chances are the second set is better IC's (and chances are the price will reflect this).

Just checked that g. skill kit your looking at and it is indeed 16-16-16 ;). Point in case. Although as most have mentioned, most will be hard pressed to notice a huge difference anyways, but hey a few more % for is what a lot of us strive for.


Edit: To answer the original question, here is a snip from my chart I made myself, it has most 3600/3800/4000 with common CAS latency. As you can see Bandwidth doesn't change between 3060C16 and C18, but latency does.
It goes from 10ns (nano seconds) with cas18 down to 8.89ns @ cas 16. Depend on the work load (random I/O vs sequential) you may notice a difference or nothing at all.

Ram TypeEffective ClockRamClock Cycle TimeCASLatencyBandwidth (MB/s)GB/s
DDR4
3600​
DDR4-3600
0.56​
18​
10.00​
28800​
28.8​
DDR4
3600​
DDR4-3600
0.56​
17​
9.44​
28800​
28.8​
DDR4
3600​
DDR4-3600
0.56​
16​
8.89​
28800​
28.8​
DDR4
3600​
DDR4-3600
0.56​
15​
8.33​
28800​
28.8​
DDR4
3600​
DDR4-3600
0.56​
14​
7.78​
28800​
28.8​
DDR4
3800​
DDR4-3800
0.53​
19​
10.00​
30400​
30.4​
DDR4
3800​
DDR4-3800
0.53​
18​
9.47​
30400​
30.4​
DDR4
3800​
DDR4-3800
0.53​
17​
8.95​
30400​
30.4​
DDR4
3800​
DDR4-3800
0.53​
16​
8.42​
30400​
30.4​
DDR4
3800​
DDR4-3800
0.53​
15​
7.89​
30400​
30.4​
DDR4
3800​
DDR4-3800
0.53​
14​
7.37​
30400​
30.4​
DDR4
4000​
DDR4-4000
0.50​
19​
9.50​
32000​
32​
DDR4
4000​
DDR4-4000
0.50​
18​
9.00​
32000​
32​
DDR4
4000​
DDR4-4000
0.50​
17​
8.50​
32000​
32​
DDR4
4000​
DDR4-4000
0.50​
16​
8.00​
32000​
32​
 
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Corsair has amazing warranty support and customer service. Would your average person tell the difference between C14 and C16 3200 ram? Google the results and you'll see, the answer is no. Not even close. If you want the extra few fps, then go for it. If you want to overclock to 3600 c16 or so, get the 3200 c14. If you are not going to overclock, buy whatever you want and set xmp and forget it.

You will not find many Corsair haters. Corsair has been around a long time and is legendary with their customer service.
Corsair has excellent support, and their ram isn't bad- it's just not the greatest ~right now~ - and especially if you're looking at high speed and low latency.
 
Corsair has excellent support, and their ram isn't bad- it's just not the greatest ~right now~ - and especially if you're looking at high speed and low latency.
While I have no experience with it, I've seen post after post with people having RAM issues and most of them seem to be Corsair RAM. It's not that the RAM is necessarily bad but Corsair will run the chips to the absolute limit which can cause problems. A lot of time what you have to do is increase the voltage over and above the XMP settings to get it stable. While no RAM manufacturer is free of compatibility problems it seems Corsair tends to have more problems than other premium RAM manufacturers.

What most people are trying to say is while Corsair RAM isn't horrible you can get better RAM for the same or lower prices. G.Skill seems to be a really popular brand with a lot of people due to good performance and few issues. I have G.Skill kits in my and my son's system and they've been working perfectly. It was the first time I'd ever used G.Skill. I had used Corsair RAM for years with no issues but when I went to build my system and my son's I did some looking and I was seeing a lot of issues with Corsair RAM which was fixed by changing to another brand, oftentimes G.Skill. I don't regret going with G.Skill instead of Corsair.
 
I don't know if it has, but seeing as their 4000 series APU's are getting > 4000mhz I hope it'll probably be similar.
 
Since the Infinity Fabric speed is tied to Mem Speed the slowest I would go for is 3733MHz RAM with the lowest latency (This was the case with Zen 2 as higher than that then the IF would run 1:2 unless you overclock the IF). I'm sure the the IF can go higher without "overclocking" but that is my suggestion.

Latency is important yes. But you need to get the Infinity Fabric up to speed too. You can't run a OC'd infinity fabric and slow RAM because of clock sync issues. The clocks have to be synced for best performance.

So for Zen 3 The fastest config (without overclocking) would be to find the fastest supported IF speed and get the lowest latency RAM to match that speed. If the max supported IF speed is 2000MHz then get the lowest latency 4000MHz RAM kit.
 
Have to add, go with Gskill. I’ve had nothing but problems the last time I bought Corsair and have sworn them off when it comes to memory. They may have been great years ago, but not any more. Mediocre at best and overpriced. Gskill has never let me down.
 
So has this rumor about Zen 3 being optimised for DDR4 4000mhz been confirmed or debunked yet?

https://www.pcgamer.com/au/amd-ryzen-5000-cpus-may-run-best-with-faster-ddr4-4000-memory/

I am not sure. Because the test system they were running on was with DDR 4 3600 no? So I really highly doubt you will be running in to performance issues there at the IF speed given you can likely get better timings and latency at that speed. I have DDR4 32GB 3200 C14 kit. That thing has run even at 3733 around 1.4v. I would hate to even pick anything else over those modules. Will test it out first before even thinking about swapping them and 4000mhz kits aren't really easy to find for gskill for 32gb (2x16GB) modules. They are all out of stock everywhere. I can run some tight timings with this kit even at 3600-3733mhz. I did decide to just settle at 3600mhz.
 
Just sold my micron E die 3600 kit and bought a Samsung B-die 4133 mhz kit for $105. Viper Steel Series. I'm only running it at C14 3400 right now because my 3600x CPU can't do 3600 bus with the new agesa BIOSes required for the Zen 3 chips. I have an absolutely dog-shit bronze sample 3600x. Can't wait for the 5600x to release, I'll be getting that. I believe the infinity fabric rumors about 4000mhz, they make perfect sense when you look at the architectural changes to the CPU. I think the goal for zen 3 will be DDR 4000 or higher if your infinity fabric supports it and as low latency as possible. Ram is cheaper than ever right now.
 
I understand that speculation is fun but we don't know anything yet. The fact is, Zen3 is a new architecture and we have no fucking idea how its going to behave with memory latencies or with memory bandwidth increases. We can speculate only that lower latencies and high bandwidth (up to DDR4 4000MHz speeds according to AMD) will be beneficial to some degree. How much remains to be seen. AMD's architectures historically benefited from lower latencies and higher memory clocks more than Intel's do, but again, we don't know for certain that will continue.

Regardless, I wouldn't plan your RAM selections until Ryzen 5000 series reviews are out.
 
I understand that speculation is fun but we don't know anything yet. The fact is, Zen3 is a new architecture and we have no fucking idea how its going to behave with memory latencies or with memory bandwidth increases. We can speculate only that lower latencies and high bandwidth (up to DDR4 4000MHz speeds according to AMD) will be beneficial to some degree. How much remains to be seen. AMD's architectures historically benefited from lower latencies and higher memory clocks more than Intel's do, but again, we don't know for certain that will continue.

Regardless, I wouldn't plan your RAM selections until Ryzen 5000 series reviews are out.

Valid points no doubt. I would argue that upgrading to higher speed ram makes a lot of sense since the memory market pricing is in freefall right now. B-die for $100 is worth it even on Zen 2 cpus because of the crazy low latency it can hit and the benefit that has to games.
 
Careful on the B Die love. I have a set of 32GB (2x16) G. Skill B-Die rated for 4000 at Cas 19. It takes 1.40v for stability at 3600 Cas 16 with SOC voltage at 1.1v. I can't tune it following the 1sumus calculator either. I'll get higher latency or it will be unstable no matter what. I had it at 3733 for a while at Cas 16, but it took 1.47v. Also, I've had two 3900x chips and one 3950x chip and none of the three would do Infinity Fabric at 1900 with that RAM. I'm running 64 GB Hynix E Die right now at Cas 16 with slower secondary timings and latency is just barely worse than the B Dies at 3600. I also only need 1.35v on the memory and 1.05 on SOC. Maybe I'll try 3800 and Fclock of 1900 with them and see. It will be interesting to try.
 
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Careful on the B Die love. I have a set of 32GB (2x16) G. Skill B-Die rated for 4000 at Cas 19. It takes 1.40v for stability at 3600 Cas 16 with SOC voltage at 1.1v. I can't tune it following the 1sumus calculator either. I'll get higher latency or it will be unstable no matter what. I had it at 3733 for a while at Cas 16, but it took 1.47v. Also, I've had two 3900x chips and one 3950x chip and none of the three would do Infinity Fabric at 1900 with that RAM. I'm running 64 GB Hynix E Die right now at Cas 16 with slower secondary timings and latency is just barely worse than the B Dies at 3600. I also only need 1.35v on the memory and 1.05 on SOC. Maybe I'll try 3800 and Fclock of 1900 with them and see. It will be interesting to try.
I have not ever found 1sumus calculator accurate or very useful. On my TR system, the calculator only goes up to 3466 for my ram in a configuration that would not even boot. I have it at 3600mhz stable as a rock. For B-Die, using the calculator gave me about 10% less performance on the Aida Memory benchmarks. Each CPU, Dram, Motherboard even, are unique and best manually configured and tested. I would only use the Calculator as a starting point. Other factors as in Bios, AMD AGESA can also change things up. Testing and optimizing ram can literally take weeks, mostly just testing the close or final settings as you do other stuff.
 
I have not ever found 1sumus calculator accurate or very useful. On my TR system, the calculator only goes up to 3466 for my ram in a configuration that would not even boot. I have it at 3600mhz stable as a rock. For B-Die, using the calculator gave me about 10% less performance on the Aida Memory benchmarks. Each CPU, Dram, Motherboard even, are unique and best manually configured and tested. I would only use the Calculator as a starting point. Other factors as in Bios, AMD AGESA can also change things up. Testing and optimizing ram can literally take weeks, mostly just testing the close or final settings as you do other stuff.
The newer AMD Agesa bios for my Asus tuf X570 made my 3600x no longer hit 3600 on the IF and I had to drop to 3400. This would bother me but I'm getting a 5600x on launch day.
 
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I have not ever found 1sumus calculator accurate or very useful. On my TR system, the calculator only goes up to 3466 for my ram in a configuration that would not even boot. I have it at 3600mhz stable as a rock. For B-Die, using the calculator gave me about 10% less performance on the Aida Memory benchmarks. Each CPU, Dram, Motherboard even, are unique and best manually configured and tested. I would only use the Calculator as a starting point. Other factors as in Bios, AMD AGESA can also change things up. Testing and optimizing ram can literally take weeks, mostly just testing the close or final settings as you do other stuff.
The safe settings in the calculator for my current RAM work great for me. The Hynix RAM seems to be very forgiving. I'm getting latency of around 71.2 ns with 64 GB of RAM in Aida. Anecdotal of course, but that's been my experience. I also have the same RAM in 32GB in another X570 board with the same settings and get around 70.4 ns in Aida.

These are the two RAM kits I'm running now:
F4-3600C16D-32GVKC
F4-3600C16Q-64GVKC

Actually, I just retested after uninstalling iCUE. Now I'm getting 69.5 ns latency in Aida with 64 GB of the RAM above:

64 GB Aida Latency Post iCUE removal.jpg
 
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During the Zen 2 launch, they only advertised DDR4 3200 mhz which is the bare minimum of the spec and if you're running your ram that slowly then you're leaving a lot of performance on the table.

The slide looks pretty damn legit.

View attachment 290665
Maybe but "good luck"??? It just doesn't fit in LOL... we shall find out soon...
 
that leaked slide says 3800 was the sweet spot for Zen 2 which is incorrect...looks totally fake, AMD is not going to write 'good luck' on an official slide

3600 was the sweet spot for Zen 2 so I bought a G.Skill 3600 32GB kit a month back...should be fine for Zen 3 even if 4000 is the new sweet spot...
 
that leaked slide says 3800 was the sweet spot for Zen 2 which is incorrect...looks totally fake, AMD is not going to write 'good luck' on an official slide

3600 was the sweet spot for Zen 2 so I bought a G.Skill 3600 32GB kit a month back...should be fine for Zen 3 even if 4000 is the new sweet spot...
Praying my b-die can hit 4000 at C16 but even if it can't, it will do C14 at 3600 mhz which is awesome too. I've also tested 4133 at defaults and 2:1 divider and they worked well for that too so I definitely got a good set.
 
Praying my b-die can hit 4000 at C16 but even if it can't, it will do C14 at 3600 mhz which is awesome too. I've also tested 4133 at defaults and 2:1 divider and they worked well for that too so I definitely got a good set.

the 3600 kit I bought last month is Samsung B-Die rated at 16-16-16-36...
 
I did some research on this for a Ryzen 3600 build a few month ago. 3600 mhz CL18 vs 3200 mhz CL16. The 3600 mhz won in most tests. There were some pretty smart people who said 3600 mhz CL16 was optimal, but those kits were more expensive at the time. I went with 3600 mhz CL18 and the performance has been great. My take is that unless you are a stickler for performance either is good. Of course, this is all speculation since we do not know how Zen 3 will perform (perhaps differently vs Zen 2), as others have mentioned above.
 
While I have no experience with it, I've seen post after post with people having RAM issues and most of them seem to be Corsair RAM. It's not that the RAM is necessarily bad but Corsair will run the chips to the absolute limit which can cause problems. A lot of time what you have to do is increase the voltage over and above the XMP settings to get it stable. While no RAM manufacturer is free of compatibility problems it seems Corsair tends to have more problems than other premium RAM manufacturers.

What most people are trying to say is while Corsair RAM isn't horrible you can get better RAM for the same or lower prices. G.Skill seems to be a really popular brand with a lot of people due to good performance and few issues. I have G.Skill kits in my and my son's system and they've been working perfectly. It was the first time I'd ever used G.Skill. I had used Corsair RAM for years with no issues but when I went to build my system and my son's I did some looking and I was seeing a lot of issues with Corsair RAM which was fixed by changing to another brand, oftentimes G.Skill. I don't regret going with G.Skill instead of Corsair.

Yeah, both my Gskill systems have been great. Got corsair stable at XMP with some work on an x370 board, but it was touchy. TR1, I have to use specific slots (not recommended) to get it stable at JEDEC. Will upgrade to G.Skill at some point on that (if I don't just throw 1.4V at it to see if that works instead), but it's ... up.

All ram manufacturers have had ups and downs. Back in the Northwood days we all bought Mushkin, as it was the fastest - haven't seen them in a long time. Then it was corsair for a while. G.Skill had good bits for a while there too. Now it's G.Skill or T-Force or a couple of others, and avoid corsair (for AMD at least). Intel - doesn't care it seems. Better IMC, less good processor.

It happens.
 
Praying my b-die can hit 4000 at C16 but even if it can't, it will do C14 at 3600 mhz which is awesome too. I've also tested 4133 at defaults and 2:1 divider and they worked well for that too so I definitely got a good set.

4000mhz at cas 16 is very tight and usually requires some serious binning. I've no doubt you can run 4000mhz just at looser timings. Before G.Skill released their highest binned 4000mhz kit at cas 15, the highest cas was 17 to give you an idea with cas 19 being more realistic.
 
I've been wondering about that myself. I got a pair of Gskil 32gb 3200mhz CAS 16 sticks last week. Wondering If I should go for the 32GB 3600mhz CAS 18 set instead.
 
I've been wondering about that myself. I got a pair of Gskil 32gb 3200mhz CAS 16 sticks last week. Wondering If I should go for the 32GB 3600mhz CAS 18 set instead.
3200 C16 and 3600 C18 is equivalent. 3600 C16 is faster, but not by much.

Keep the existing RAM unless you want to go through all the hassle.

FWIW, my 32GB 3200 C16s kits are all doing 3600 C16
 
that leaked slide says 3800 was the sweet spot for Zen 2 which is incorrect...looks totally fake, AMD is not going to write 'good luck' on an official slide

3600 was the sweet spot for Zen 2 so I bought a G.Skill 3600 32GB kit a month back...should be fine for Zen 3 even if 4000 is the new sweet spot...
Before Zen 2 launched, weren't there plenty of slides showing that 3600 was the sweet spot? I remember one from AMD showing the latencies achieved across several RAM configurations with 3600 highlighted.

Here it is, June 19, 2019:

Screenshot_20201020-071637_Samsung Internet.jpg
 
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