5100CL17 on Z790

https://i.imgur.com/ocN9FI5.jpg

Got the MSI Z790 Tomahawk setup, somehow managed to stabilize 5105 CL17 on my Micron B die DDR4.

1.71v dram, 1.55v VDDQ, 1.35v SA.

I was going to get a 13900K initially, but with both Raptor Lake S leaks, and other users 13900K OC results, I'm getting a 13600KF for now, bin it and either upgrade to the S refresh or move onto DDR5 sooner with meteor lake (13900K / KS are pushed to their limits out of the box, very little OC headroom and a lot of users degrading them fast without much OC, and I don't even need anymore than a 13600K for 4K).

The latency is rubbish because of G2, somehow worse than my 4800 / 4900 results from the previous board, maybe because the new board doesn't auto tune tertiary timings as well as the previous one.

My current 12600K only plays nice with 3800G1, and I can get this ram to run at 4133CL14, so I need to get a 13600K / KF that can run just 4133 G1 now. From user results on OCnet, all 13th gen chips so far can manage 4133 G1 so the first one I get should hopefully be fine.

So I got my 13600KF earlier, somehow I got super lucky with an early batch, it boots but wont stabilize 4400 G1, but can run 4300CL15 stable.

I spent a while testing for CL14 max stability, someone on OCnet has managed 4300CL14 1.72v with 4 sticks of this but with water cooling.

On air, I can 'only' get 4266 to stabilize with 1.72v, tried up to 1.75v but 4300CL14 simply won't stabilize.

Between testing since the 10900K with this kit, it simply looks like scaling completely stops at 1.725v, going above that does nothing for it.

DDR4 wise, latency is always worse with this IC than Samsung B die as the trfc won't go anywhere near as low.

So running it at around 1.72v, it can do 4266CL14, 4533CL15 and 5100CL17 on air, I already spent a long time trying to stabilize 4800CL16 but it wouldn't, so it looks like somewhere between 4700-4800 for CL16.

Still very nice ram, although its been discontinued now and no longer available in 2x16.

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Now for higher clocks in G2 and DDR5 specifically, you need to DOUBLE the frequency to match the latency of G1, also DDR5 has double the calculations per cycle so treats its CL value as half.

To match DDR4 4000CL16 G1 latency in G2, you need to reach 8000CL32 on DDR5! To match 4266CL14, you need 8533CL28!!!!

Of course higher frequency = much more bandwidth, but 99% of stuff benefits from latency over bandwidth.

Needing to run gear 2 to stabilize higher ram frequencies is basically what kills the gains, and why DDR4 vs DDR5 performance is so insignificant (6000CL32 G2 DDR5 is around 0.8% more average performance than 3600CL16 G1 DDR4).

Right now though, DDR5 is finally cheap, if you buy a cheap Hynix M de kit, you can overclock it to around 7000 - 7400 with super tight latencies and match most DDR4 latency.

However all this is exclusive to 2x16 setups, 32 Gb isn't going to be enough for long, soon even games will start utilizing 64 Gb.

Currently any setup with 64 Gb DDR5 is just pure crap for performance, 2x32 DDR5 maxes out at around 6400, as for 4x16 no one can even get XMP values to run and it needs reducing all the way to 4000-4400 while still being stuck in G2 because DDR5 cannot run in G1!

What we need next is 32 Gb SR and 64 Gb DR kits on DDR5 for it to be significantly better than DDR4! Hopefully these will happen in 2023 prior to Intel 14th gen, but until then I'll be sticking to this setup.

4266CL14 G1 on the new 13600KF:

https://i.imgur.com/s0DStOD.jpg


Still tuning the rest of the timings.

And nvm, 4300CL14 working after adding a fan:


https://i.imgur.com/aqOjZ1e.jpg


Temperature on the hotter module dropped from 59c to 43c max with this simple trick:

https://i.imgur.com/fWGqqCe.jpg