Question Very high latency on DDR4 RAM

[shadeware]

Hi, I got two of 16GB Patriot Viper Elite II DDR4-4000 for cheap, there's a review of it: https://www.tomshardware.com/reviews/patriot-viper-elite-ii-ddr4-4000-c20-review
In review they were able to get 18-25-25-45 at 4000hz and 1.45V, which would be nice enough for me.

My environment: Ryzen 5950x, ASUS X570 PRO with last BIOS, Ryzen Master, DRAM Voltage 1.5V.

On the bright side, I was immediately able to get it to 4000hz even though I use AMD and should be limited by IF, but default timings were near 30 so I started to tighten them.
In the end, I was able get 21 CAS Latency as 3800hz and was not able to get 20 CAS Latency even at 3200hz, which is awful.
Interestingly, I accidentally used decoupled mode with 3800Hz memory and 1800Hz IF and was able to get stable 16 CAS Latency but it turned out to be slower. Also, CAS Write Latency works at 16 cycles.

So, my decoupled and write CAS Latency are cool but real CAS Latency is diappointing. Is this a problem with RAM itself or can I try to do something about it?


UPD: this helped me
> Increase SOC to 1.125 V, VDDP to 1.00 V, and VDDG CCD to 1.00 V

UPD2: got to 67ns with this:

Still, 67ns is a bit higher than I expected. Would it be safe to increase voltage further to 1.55V or even 1.6V if I have air tower (dark rock pro 4)?
UPD3: overclock with tCL=17 tCWL=14 is pretty stable (survives 1 hour of OCCT) but tCL=17 tCWL=16 never POSTs. How is that possible?

 

[white.a.drew]

Hi, I got two of 16GB Patriot Viper Elite II DDR4-4000 for cheap, there's a review of it: https://www.tomshardware.com/reviews/patriot-viper-elite-ii-ddr4-4000-c20-review
In review they were able to get 18-25-25-45 at 4000hz and 1.45V, which would be nice enough for me.

My environment: Ryzen 5950x, ASUS X570 PRO with last BIOS, Ryzen Master, DRAM Voltage 1.5V.

On the bright side, I was immediately able to get it to 4000hz even though I use AMD and should be limited by IF, but default timings were near 30 so I started to tighten them.
In the end, I was able get 21 CAS Latency as 3800hz and was not able to get 20 CAS Latency even at 3200hz, which is awful.
Interestingly, I accidentally used decoupled mode with 3800Hz memory and 1800Hz IF and was able to get stable 16 CAS Latency but it turned out to be slower. Also, CAS Write Latency works at 16 cycles.

So, my decoupled and write CAS Latency are cool but real CAS Latency is diappointing. Is this a problem with RAM itself or can I try to do something about it?


UPD: this helped me
> Increase SOC to 1.125 V, VDDP to 1.00 V, and VDDG CCD to 1.00 V

UPD2: got to 67ns with this:

Still, 67ns is a bit higher than I expected. Would it be safe to increase voltage further to 1.55V or even 1.6V if I have air tower (dark rock pro 4)?
UPD3: overclock with tCL=17 tCWL=14 is pretty stable (survives 1 hour of OCCT) but tCL=17 tCWL=16 never POSTs. How is that possible?

Are these ram sticks from a single kit, or two separate matching kits?

 

[shadeware]

Separate kits. In Taiphoon only date and serial are different.

 

[klavs]

I wouldn't use DDR4-4000 for an AMD CPU, which has been reported by many as being problematic. I would get DDR4-3600 CL14, which has a slightly faster latency than the DDR4-4000 CL18.

This kit should be compatible with your motherboard, but I am not 100% sure:

F4-3600C14D-32GTZN-(EOL) - Specification - G.SKILL International Enterprise Co., Ltd.

Trident Z Neo DDR4-3600 CL14-15-15-35 1.45V 32GB (2x16GB)

www.gskill.com

Check the compatibility list for the RAM or the motherboard.

 

[shadeware]

> I wouldn't use DDR4-4000
I never intended to and overall I expected that I'd buy 4000Hz DRAM and by running it at ~3600 will get good timings. Aparrently it does not work this way.

Alright, thank you for replies, I'll try to return this DRAM because it's from different kits and has horrible timings.

> F4-3600C14D-32GTZN
This one is too expensive, I found these decent options near my place: F4-3200C14D-32GVR and F4-3600C16D-32GVKC. Which one of them should be easier to overclock to 3600 CL14 (and possibly further)?

 

[klavs]

F4-3200C14D-32GVR and F4-3600C16D-32GVKC. Which one of them should be easier to overclock to 3600 CL14 (and possibly further)?

No idea. I usually just buy the best that I think is worth the money and use the recommended settings. The time it takes for me to OC cheaper RAM = time that I can spend earning money for more expensive RAM. I used to OC many years ago, but today I only undervolt and underclock the CPU and GPU.

Games that don't preform on modern system, I ignore them. I wont support games that don't run at 120+ fps on 8 gigs of VRAM. If they don't implement settings that can run on a low end GPU ($450), then they don't deserve my money, even when I've got 24 gigs VRAM.