RAM Speeds vs Timings/Latency

[Char170]

I'm looking to build a new higher end pc and I want to understand RAM specs better.

 

What is the differences that I'd see between two types of RAM?

 

I have been looking at Corsair Vengeance 2x16 @ DDR4-4000 with timings of 18-22-22-42

 

But that has higher timings compared to something like:

G.Skill Trident Z 2x16 @ DDR4-3866 with timings of 18-18-18-38  (and about $35 cheaper)

 

So what is the differences here. What programs would benefit from higher frequency and which from lower timings?

 

(For reference this is the build I am currently looking for)

[Jurrunio]

Frequency affects bandwidth significantly and timings somewhat little, but combination of frequency and timings give you latency. Games care about latency a lot on Ryzen, but only some work (like crypto mining for example) care about bandwidth that much (above a certain point of course, say 3200MHz).

 

These two kit could be different in model of memory in it, but 3866 18-18-18 isnt tight enough that I can guarantee it will be anything certain.

[Hairless Monkey Boy]

Timings and freq are linked. They are not independent. You can do a simple equation to determine the real latency based on the freq and timings.

 

For the top kit:

 

18CL/(4000MHz/2) = 9.0ns CAS latency

 

For the bottom kit:

 

18CL/(3866MHz/2) = 9.3ns CAS latency

 

Aside from that, you have to think about your preferences and expectations. The best option for someone who does not want to have to fiddle with memory timings and frequencies and voltages would be to get a simple good kit of 3600Mhz CL16 RAM like these:

 

$165:

https://pcpartpicker.com/product/w3FKHx/gskill-trident-z-neo-32-gb-2-x-16-gb-ddr4-3600-memory-f4-3600c16d-32gtznc

 

If you think you might want to try to OC the memory on your own at a later date then maybe something like this would be better:

 

$235

https://pcpartpicker.com/product/6z6qqs/gskill-trident-z-rgb-32-gb-2-x-16-gb-ddr4-3600-memory-f4-3600c16d-32gtzr

 

If you want the fastest RAM and you want to customize your voltages and timings then you might even try some more expensive RAM like this:

 

$380

https://pcpartpicker.com/product/8jZFf7/gskill-tridentz-rgb-32gb-4-x-8gb-ddr4-4000-memory-f4-4000c17q-32gtzr

 

Honestly, the performance doesn't change much past 3200Mhz, so with your build and level of knowledge I'd recommend something more like the first kit I linked.

 

 

[pipnina]

I have been wondering this myself. I have a 3000Mhz 15-17-17-35 32gb kit in my system, and it goes up to 3.2Ghz without timing changes just by me upping the multiplier a bit more. This is with the ram being run at 1.36v according to my motherboard's live bios sensor.

I don't know how much further I can realistically push the kit on voltage since I read somewhere that DDR4 doesn't like going above the 1.35 it must already be configured for. Although I can see the timings are relatively tight by default, I am worried an upgrade to Zen3 from my rather ram-apathetic 6700k would be squandering some performance if I can't push it a little further.

[Hairless Monkey Boy]

@pipnina

 

I have my DDR4 running @ 1.45V daily. Up to 1.5V is fine for daily if there is a benefit. With good airflow and higher end dimms you could go even higher, maybe 1.55V if it provides better performance.

 

15-17-17-35 @ 3200MHz isn't really that tight. Pretty average imho. If you want to find out what your kit is capable of, you could start by setting the voltage to 1.45V, and loosening the timings to something like 18-20-20-40 (play around with it) and seeing how high you can get with freq. When you hit a wall you can try loosening the timings again. Once you find your max clock, you can work on tightening the timings. From there you would reduce the clocks and timings until you find the combination that gives you the best real latency as I calculated above. And then you could fiddle with reducing the voltage if you wanted to. 16-19-19-36 @ 3600MHz might be within reach with a voltage bump.

 

It's a lot of work and a lot of trial and error for not that much performance increase, though. At 3200MHz you'll be getting most of the performance out of Zen 3.

[pipnina]

1 hour ago, HairlessMonkeyBoy said:

@pipnina

 

I have my DDR4 running @ 1.45V daily. Up to 1.5V is fine for daily if there is a benefit. With good airflow and higher end dimms you could go even higher, maybe 1.55V if it provides better performance.

 

15-17-17-35 @ 3200MHz isn't really that tight. Pretty average imho. If you want to find out what your kit is capable of, you could start by setting the voltage to 1.45V, and loosening the timings to something like 18-20-20-40 (play around with it) and seeing how high you can get with freq. When you hit a wall you can try loosening the timings again. Once you find your max clock, you can work on tightening the timings. From there you would reduce the clocks and timings until you find the combination that gives you the best real latency as I calculated above. And then you could fiddle with reducing the voltage if you wanted to. 16-19-19-36 @ 3600MHz might be within reach with a voltage bump.

 

It's a lot of work and a lot of trial and error for not that much performance increase, though. At 3200MHz you'll be getting most of the performance out of Zen 3.

Thanks for the tips! It might only ammount to 1-5% over my normal 3GHz XMP in games, but free performance is free performance!

I think the cooler I am thinking of for the Zen3 processor I'm planning on will probably help with airflow over the ram too (noctua u14s) since my dark rock 3 sucks air from over the top of the ram currently.

[Hairless Monkey Boy]

5 minutes ago, pipnina said:

Thanks for the tips! It might only ammount to 1-5% over my normal 3GHz XMP in games, but free performance is free performance!

I think the cooler I am thinking of for the Zen3 processor I'm planning on will probably help with airflow over the ram too (noctua u14s) since my dark rock 3 sucks air from over the top of the ram currently.

You could get a lot more performance by tuning your secondary timings, most importantly tRFC(as low as you can) and TREFI(as high as you can up to 65535). Those two settings alone could make a big difference since they together control for how long and how often, respectively, your DRAM is refreshing rather than reading and writing. If you are interested, here is a great thread on memory OCing:

 

 

[MADRAFi]

I bought a hyperx 2 x 16GB 3600 CL17-21-21-21-39 (HX436C17FB3K2/32) sticks for Ryzen 5800x. I put them on ASUS Strix x570-E Gaming.

It seems there is a problem with correct XMP profile read. The best what I could configure was 3600Mhz @ CL18-21-21-41-87. Either this RAM is faulty or x570 has issues reading sticks correctly. Nominal timings were possible only at 2400Mhz. Any suggestions?

 

I have also tried same sticks on MSI x570 motherboard. Similar result. and different sticks Patriot Viper 2 x 8GB

 3733 @ CL17 which also gave CL18 after windows boot in CPU-Z.

 

If I buy different G.SKILL sticks which are 2x 16GB Will I also get CL18 instead of CL16?

 

 

 

 

I am attaching also another screen with result after first run with all defaults except XMP profile

[Guest]

Go to the sub timings menu and disable "Gear Down mode" and it will run the odd ball cas latency of 17. 

 

[MADRAFi]

23 minutes ago, ShrimpBrime said:

Go to the sub timings menu and disable "Gear Down mode" and it will run the odd ball cas latency of 17. 

 

Thanks a million that helped!

[MADRAFi]

Is Command Rate 2T expected for such timings?

NVM, configured it correctly now.Any tips to tune it more greatly appreciated. 

 

[Guest]

33 minutes ago, MADRAFi said:

Is Command Rate 2T expected for such timings?

NVM, configured it correctly now.Any tips to tune it more greatly appreciated. 

 

Sure. The main timings you see here, tighten them. Do one at a time and test. Keep the 1T command rate. Be sure the memory voltage is set to 1.36v instead of 1.35v to accommodate for any v-droop. You also can disable power down mode, this will help prevent the memory from throttling/power saving.

[MADRAFi]

I will have to work on it. So far with 1T and these above settings I got blue screen immediately after heavy load from the game.

 

[Guest]

1 hour ago, MADRAFi said:

I will have to work on it. So far with 1T and these above settings I got blue screen immediately after heavy load from the game.

 

OK, switch back to 2T (which helps with stability in most cases) and test again. 

[MADRAFi]

8 hours ago, ShrimpBrime said:

OK, switch back to 2T (which helps with stability in most cases) and test again. 

I am back on 1T. your suggestion to make sure the is no variation with voltage and is set to 1.36 helped. Is it my impression or lower CL is better then higher memory speed?

Which timing should be changed when I increase memory speed from 15-17-17-36-69-1 on 3000 Mhz

[Guest]

1 hour ago, MADRAFi said:

I am back on 1T. your suggestion to make sure the is no variation with voltage and is set to 1.36 helped. Is it my impression or lower CL is better then higher memory speed?

Which timing should be changed when I increase memory speed from 15-17-17-36-69-1 on 3000 Mhz

You would loosen the Cas latency, but try and keep the same timings and increase frequency until unstable. 

[MADRAFi]

10 minutes ago, ShrimpBrime said:

You would loosen the Cas latency, but try and keep the same timings and increase frequency until unstable. 

I am now back with 2T and XMP. Default XMP 3600MHz is unstable on 1T under load. Will play more with different XMP profiles (have 2)

[Guest]

5 minutes ago, MADRAFi said:

I am now back with 2T and XMP. Default XMP 3600MHz is unstable on 1T under load. Will play more with different XMP profiles (have 2)

It will take some trial and error. But you're on the right track. Most anything that happens next is up to you. Small changes are best.