Tabbed traces vs shielded traces on z490 boards - Overclock.net - An Overclocking Community

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Tabbed traces vs shielded traces on z490 boards

 
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post #1 of 2 (permalink) Old 05-25-2020, 10:37 PM - Thread Starter
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Tabbed traces vs shielded traces on z490 boards

As the title says I am curious as to the potential memory overclocking performance, or more specifically signal quality/integrity of the two different approaches that z490 MB vendors have taken to take memory overclocking to the next level, as far as MB's go, which along with the SL of your IMC is often the limiting factor.

MSI is using a 6 layer PCB with tabbed traces for nearly all of their z490 boards (with the exception of the ITX unify and the Godlike, which are also using tabbed traces just with a slightly different memory topology)
They are advertising speeds of 4800 MT/S with 4 DIMM slots on any of these boards, all the way down to the cheapest $160 z490 they make. All on the same 6 layer PCB, which is really nice, and for 4 DIMM boards this is highly impressive.

There is a white paper explaining why and how the tabbed traces lead to better signal quality through cross-talk mitigation and impedance management:
https://duckduckgo.com/l/?kh=-1&uddg...ment-paper.pdf

Gigabyte however is taking a seemingly different approach also with a 6 layer PCB, but placing the memory traces between 2 very thick shielded ground layers. Unknown whether they are using tabbed traces between the ground shields for memory traces or not. I wouldn't rule it out, but they are not advertising it.
They are however advertising speeds of 5000 MT/S also on 4 DIMM boards which is extremely impressive as well. From my understanding they could potentially go even higher as after 5000 you run out of XMP profiles, but this is purely speculative, and depends on many other variables. But assuming your memory controller and memory kit are up to it, it sounds like perhaps the MB might not be the limiting factor. Same goes for MSI I suppose.
I cannot find any real highly technical info on GB's methods, whereas MSI's tabbed trace method has a full white-paper on the subject.
The best I can find is a basic description/visual in the attached image.

I am curious if anyone has any insight as to which of these methods are going to be more effective in the areas where it matters (trace signal integrity, and therefore ability to perform high frequency with stability and low latency timings)
Various reviews on the boards in question have only left me with more questions than answers.

The boards I am considering are the z490 MSI Gaming edge wifi, and Gigabyte Vision-G and/or Aorus Elite. Vision-G comes with the extra PCIE slot at the bottom which is particularly handy for me, but I could make any of these boards work if there is a reason to choose one over the other.
Thanks in advance!
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post #2 of 2 (permalink) Old 07-22-2020, 09:43 PM
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It's impossible to tell which is better just based on the description. Running the traces on the top layer implies microstrip transmission line. Inner layer is probably a stripline structure. There are pros/cons to both. Since the conditions are unique to each board, it's hard to say which is better without a several examples of each type and signal integrity measurements. For example, Gigabyte might have had to bury the traces due to EMI issues that MSI aren't experiencing on their board.

In general, I would say the traces routed on top layer are usually more ideal as a transmission line except for EMI performance. The layer switch from top to inner layers will always introduce an impedance discontinuity.

In short, I would not base your decision based on one aspect of how they routed their DDR4 interface. The proof will be in the results; if they perform / OC similarly in reviews then I would pick the board you like better based on other factors.
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