Help Reducing Memory Latency 4133 15-15-15-30 2T (can't break AIDA64 50 ns)

[iProSocial]

Hi all,

Long time gamer, first time poster.

I've been fiddling with my RAM timings for for days, and I don't know where to go from here. 

Thought I'd see if someone in the Rookies thread can help me out.

My goal is to get my latency (AIDA64 Extreme ) below 50 ns, I dream of 45-46 ns. But is that just what it is? A dream?

Current AIDA64 Latency ~ 51.8 ns
Stable at 4133 with 15-15-15-30 RFC 260

Specs and OC

 

(TestMem5 anta777 5 Cycles PASS)
(secondaries and Tertiaries are in the screenshot).

Kit: GSKILL Trident F4-4266C17D-32GTRSB

RTL : I thought I had tightened the RTLs, but it looks like I only have them at 73/73/73 | 81/81/81
(Can't find iO-L timings in my BIOS to fiddle with them) 

Board: z690 Edge DDR4
VCore: 1.325 v
DRAM Voltage: 1.5 v
SA Voltage: 1.42 v
VDDQ: 1.35 v

What can I do here to make an impact on my Latency?

Hope I've provided enough info, and hope someone can give a guiding hand.

 

[wutske]

No experience with DDR4, so I had a look at some top results and it's not impossible ?

45.8ns -> https://hwbot.org/submission/4828598_ai20g_aida64___memory_read_ddr4_sdram_87280_points

43.4ns -> https://hwbot.org/submission/4833339_noliso_aida64___memory_read_ddr4_sdram_86853_points

 

I don't know what you've already tried, but I would at least try to get the command rate on 1T if your motherboard allows it (make sure to double check it because I've had boards that had 1T in the BIOS but ultimately ran at 2T). It might be that your RAM at these settings is not stable at 1T anymore, so you might need to loosen some other timings (or increase VDDR a bit).

Your BCLK also seems a tad low, do you have "spread spectrum" enabled in the BIOS, this usually causes it to drop by a tiny percent (and you're only 3,5% away from 50ns). Upping the BCLK just a few MHz might also help closing the gap.

[iProSocial]

Thank you for your response @wutske. Much appreciated.

It seems from my testing that my board won't allow 1T a this high of a frequency (4133). 

I did have 1T running previous with with following frequency and timing: 

Frequency: 3600 MHZ
Primary timings: 14-13-11-21

Perhaps I can revisit 1T and try going up from 3600 with looser timings. Thanks for that suggestion.

And thanks for catching that reduced BCLK. I hadn't researched that frequency before, and now I see that drop from the 100 MHZ set in bios.

And now I know what "spread spectrum" is and what it does. 

I tried increasing by .24 to make up for what was missing, but experienced instability. I did not however try disabling Spread Spectrum.

I did see a slight increase in RAM and CPU frequency from that increase. I guess that's how people are able to get those non-standard RAM frequencies I see online.

I did order a z790 Apex and some 8000 MHZ DDR5. I bet THAT board will allow me to play a little more with BCLK with better stability.

I just don't know what else my z690 Edge can give me.

Thanks again, and let me know if there's anything else you think I can try.

 

 

[wutske]

Yes, CPU and RAM frequencies are all tied to the BCLK. CPU frequency is the BCLK times a multiplier (in your case, the default multiplier can be between 8x and 55x, depending on load, temps and turbo limits). The memory speeds are determined by a ratio (most BIOSes just show you the frequency instead of the rather unpractical ratio's like 1:31, 5:4, 3:4, ...).

Since we're talking about latency alone, it might be that at a lower frequency, with much tighter timings you could get a better score, its all about finding the balance.

 

It's strange though that only a .24Mhz increase causes instability, either you're already at the edge of the CPU at that voltage, or there's an odd wall you're hitting. Did you set the PCIe frequency to 100MHz? Some GPUs/motherboards can be really picky about the PCIe frequency, but still, being off by <1% and causing problems is oddly sensitive.