What is the lowest DDR3 RAM latency I can achieve WITHOUT XMP?

[Greg136]

Recently I replaced the Samsung M378B5273DH0-CK0 DDR3 1600MHz C11 2x4GB in my Dell OptiPlex 7010 with Corsair CMV16GX3M2A1600C11 ValueSelect DDR3 1600MHz C11 2x8GB.

 

I have lost FPS in games like World of Tanks (1440p 110 average fell to 90 average, and drops as low as 60 sometimes which didn't happen with the Samsung RAM.) A little bit stuttery when flicking the camera around in other games. Both CPU & GPU rarely go above 50% utilisation.

 

I ran some tests and RAM latency has increased from 70 ns with the old setup to 85.3 ns. Could this be the reason why average FPS has fallen, varies more, and the image occasionally gets tearing?

 

Running all four of those sticks together for a total of 24GB the latency has gone up to 87.5 ns. Is this due to increased load on the memory controller?

 

My second question is can I run C10 or even C9 RAM on this Dell motherboard (0KRC95) that does not support (afaik) manual memory overclocking nor XMP. I was about to buy some (used) Corsair Vengeance Pro 9-9-9-24 and then I read that to achieve the labled timing, it relies on XMP - otherwise it will run at 1333MHz. Is this true?

 

If possible, I would like to find some low latency RAM that does not need overclocking out the box. I want to run ram at the highest speed supported by this dell motherboard - 1600MHz.

 

(please note:

before anyone suggests "just buy a new PC", please don't. I appreciate its already had it's tenth birthday & comes with many limitations, but this system still has some use left in it & will be capable for a few more years)

 

System Info

Dell OptiPlex 7010

Intel Core i7-3770 3.4 GHz

Samsung 870 QVO 1TB boot drive

Zotac RTX 2070 Super Mini

Windows 10 Pro 22H2 64-bit

[Eigenvektor]

Lowest possible latency without XMP (or manual overclocking) would need to follow JEDEC specifications for DDR3. For that, see this table: https://en.wikipedia.org/wiki/DDR3_SDRAM#Modules — Manual overclocking, as always, is silicon lottery.

 

Just keep in mind that latency is measured in clock cycles, so the same number means different things at different clock speeds. For example CL9 at 1333 MHz translates to a (theoretical) absolute latency of 13.5 ns, while CL9 at 1600 MHz translates to 11.25 ns.

 

~edit: https://www.findlaptopdriver.com/0krc95-dell/

According to this, the board only supports DDR3 1333 and 1600 MT/s. So the fastest RAM running at JEDEC approved speeds should be PC3-12800 Type "G" with 1600 MT/s and CL 8-8-8. Assuming you can find sticks of that type on the used market and the board doesn't have any other limitations.

 

1 hour ago, Greg136 said:

Could this be the reason why average FPS has fallen, varies more, and the image occasionally gets tearing?

Yes, slower RAM can cause decreased performance if the engine happens to be memory bound.

 

Screen tearing depends on the combination of your monitor's refresh rate and the game's fps. To get rid of tearing completely you need to use either VSync or Adaptive Sync (to synchronize card and monitor). But it may be less noticeable at certain fps without it (e.g. if fps happens to be some multiple of monitor Hz)

[Greg136]

Thank you @Eigenvektor for the detailed reply!

 

The board is definitely running RAM at 1600MHz. Additionally, it actually has 2x SATA III and 2x SATA II & my GPU is actually running at PCIe 3.0 x16, not the 2.0 max stated by https://www.findlaptopdriver.com/0krc95-dell/. (more of a general comment, since I appreciate you taking the time to help me) But yeah, different websites have given me incomplete & misleading info about this motherboard... probably since it is so old and average they don't bother to check the info.

 

I actually have a G-Sync compatible display, and I wrongly assumed it was working automatically in the background. I'm connected with HDMI at the moment and the 2.0 standard supported by the GPU does not include VRR. I will fish out the DisplayPort lead that came with the monitor and try to enable VRR.

 

I will run some more tests on my original Samsung RAM soon, for consistency... then I might be able to decide if it is worth bothering to buy some other low latency RAM.

 

I didn't find 8GB of RAM to be too limiting in the first place, and I kinda just thought that 16GB would be a straight upgrade. Too bad I didn't know about the troubles with latency and clock cycles and all that in the first place haha.

[Echothedolpin]

Most optiplex systems will accept low latency memory but will run it at a higher latency. My experience is anecdotal (somewhere between 6-10 ddr3 era systems) it was never worth getting lower latency memory in any case I came across.