Memory timings using DOCP

ubern00b · 22 Jan 2020 at 09:43

Hi all

I have this memory kit:

https://www.overclockers.co.uk/patr...dual-channel-kit-pvs416g360c7k-my-104-pa.html

On an ASUS X470-i with a 3700x. I have enabled DOCP in the BIOS but the timings are not what they should be.

CL is showing as 18 instead of 17 (in the BIOS it shows as 17) and tRC is 84 but should be 68. I am fully aware I can change these settings myself in the BIOS but since CAS IS already set to 17 in the BIOS but showing 18 in Windows, any idea what is going on here? Setting to 16 (1.35v) causes a non-POST and I have to clear CMOS.

Showing the SPD timings:

Joxeon · 22 Jan 2020 at 10:18

If gear down mode is enabled this means only an even CL can be used. you could try disabling it but then it might not be stable, alternatively you could try setting a CL of 16 with GDM mode on.

ubern00b · 22 Jan 2020 at 10:21

That would certainly explain it! Thank you

Space Monkey · 22 Jan 2020 at 16:37

ubern00b said:
That would certainly explain it! Thank you

I'm glad you posted this as I've got the same issue but couldn't find an answer as to why? I'll have a look in the BIOS later on

GregI · 23 Jan 2020 at 00:10

I'm in a similar boat. I see 2 options here due to how the motherboards work, well mine anyway. You cannot have a command rate of 1T while gear mode is disabled. My PC barely boots into Windows before erroring

You either run gearmode off and have your specified timings with 2T as command rate OR You run gearmode on with 1+ CAS but 1T

If anyone can do some game benchmarks to see what's faster that would be great.

Joxeon · 23 Jan 2020 at 10:29

GregI said:
I'm in a similar boat. I see 2 options here due to how the motherboards work, well mine anyway. You cannot have a command rate of 1T while gear mode is disabled. My PC barely boots into Windows before erroring

You either run gearmode off and have your specified timings with 2T as command rate OR You run gearmode on with 1+ CAS but 1T

If anyone can do some game benchmarks to see what's faster that would be great.

The best option would be leaving gdm on and setting cas at -1, may need to up the voltage a bit to get it stable.

Murphy · 23 Jan 2020 at 12:45

GregI said:
If anyone can do some game benchmarks to see what's faster that would be great.

I posted this in another thread but AMD did some testing and if you have faith in vendor benchmarks they show little difference, about 1-3% between 1T GDM off vs on.

GregI · 23 Jan 2020 at 13:42

Joxeon said:
The best option would be leaving gdm on and setting cas at -1, may need to up the voltage a bit to get it stable.

The thing is the memory I got was in the QVL and ran at CAS 15 but it didn't show CR so I am unsure if they somehow got 1T non GDM at CAS 15 or if they never checked GDM was on and it was 16.

Murphy said:
I posted this in another thread but AMD did some testing and if you have faith in vendor benchmarks they show little difference, about 1-3% between 1T GDM off vs on.

The thing is when I'm going for high frame rates, I should just leave GDM on to get 1T then?

Joxeon · 23 Jan 2020 at 13:54

GregI said:
The thing is the memory I got was in the QVL and ran at CAS 15 but it didn't show CR so I am unsure if they somehow got 1T non GDM at CAS 15 or if they never checked GDM was on and it was 16.

The thing is when I'm going for high frame rates, I should just leave GDM on to get 1T then?

It was probably always 16 as gdm defaults as on in ryzen systems where ram is over something like 2666.

Gdm off at the Same timings will be slighty better, that said if gdm on means you can tighten timings further then it can be better than loser timings with gdm off.

You should download aida 64 and run the latency benchmark as latency is most important for games and this will help you see how the changes you make in timings are affecting latency.

GregI · 23 Jan 2020 at 21:28

Results with AIDA64:

GDM Off: https://i.imgur.com/VCDhYz6.png
GDM On: https://i.imgur.com/AMiFUct.png

GDM Off seems to win in every test besides 3