BIOS 1703 still slow for memory, doesn't save all CMOS settings to file, 8 reboots to flash...

[ttesty_1]

Maybe I bought too soon, but before the China tariffs! X870E Taichi w/9950X3D please...!  Or wait for Panther Lake.

[Chainbold]

For the sake of good order, I replicated your settings, memory at 6400 and your timings. I get a very similar result. This is what you get with DDR 5 6400. If you want to see the latency that other users are getting with their Z890 boards, e.g. in the lower 70 or upper  60, you need much better memory. 

[ClearedIn2Bravo]

Well ya, running stock 6400, and likely stock fabrics and cache, that is what you can expect. 

[ttesty_1]

Much better memory than Trident Z5? Everyone posts timing hacks that eventually prove unstable.

[Chainbold]

Has nothing to do with the vendor name, or the BIOS version.  According to your screenshot, your RAM is running at 6400 MT/s at CAS 32.  Memory latency is resulting from a combination of both, frequency and CAS, while frequency is the main driver. With DDR 5 6400, you get what you get. You need "better" RAM to get lower latency. Simple as this. 

[ClearedIn2Bravo]

Most people are not running unstable memory configs. Plenty of us on here run very hard stability tests, and then actually go use our rigs and flesh out stability. I've been running 8600 CL38 on my 285K/Apex build since it released without a single issue or crash. That is because I spent a couple days, tuning and testing until I found an Arrow Lake sweet spot for my chip/setup and comfort zone with IMC/VCCSA voltage. 

More importantly you also have to tune up the D2D/NGU and Cache to get latency down. Again it does not cause instability doing so. 

6400 CL32 would be slow even by Alder Lake standards, and I'm not trying to be a jerk, just tell you what you need to run if you want to see the high 60ns latency that many tuners are getting on ARL. 

Set your cache to 40-42x and D2D/NGU to 32x on both as a starting point. That should lower your latency down a bit. 

[Chainbold]

Completely agree

[ttesty_1]

So I have to fiddle with hacks (D2D/NGU, ICC, VDD, VCCSA, "Cache", etc), wait for BIOS compatibility with future RAM (96GB @ 9200 MT/S stable at stock) if there are still BIOS updates then, and pray that I don't get crashes. Latency is largely a symptom of the architecture (remote memory controller and PHY).

[Chainbold]

errr no. The low latency you get with your DDR 5 6400 is mainly due to the fact that your memory is DDR 5 6400. As explained, memory latency is a function of frequency and CAS. The RAM frequency is the main driver. D2D is helping, but is a minor factor. And you do not need any "hack" to change D2D. Even a housewife could change the D2D multiplier in BIOS.  And even this, you don't have to to do, in case you use XMP Tweaked. Why? Because "XMP Tweaked" is setting D2D automatically to x32. Multiple user here have posted their results with Z890 boards, showing memory latencies in the low 70ies, or even 60ies - with the appropriate memorys such as DDR 8600, 8800 or 9000.  I'm at 70 with CUDIMM 8800, and I do not need any "hack" for this.🙂

[extreme]

 "XMP Tweaked" is setting D2D automatically to x32"

No that is not true. 

Also you will get bsod or unstable system if you set d2d to x32.....