Calculating length for "tune length" in case of Y shape traces

Layout
1

I have 2 memories on the same 8-bit databus (with separate chipselects), so Y shape data tracks are used. When I length-tune, the principles of length calculation is not crystal clear for me.
See the printscreens:
Memory 1 is top left, memory 2 is bottom left, memory controller on the right.

I push “7” (hotkey for length tune single track), I hover over the track and length is displayed.

Length calculation to Memory1:

TuneLength1
TuneLength1886×846 211 KB

Calculation for memory 2:

TuneLength2
TuneLength2845×797 191 KB

These are fine.

But for another track:

TuneLength4
TuneLength4795×837 180 KB

but what I’d like to see:

TuneLength3
TuneLength3795×837 179 KB

So my question is: how does algorithm select segments of a Y-shape track? How to modify this behavior? The only workaround is to separate the segemnts at the central via, measure all 3 segments individually, do the length-tune, then reconnect the parts…not too comfy:/

2

This actually looks like a bug - the route-finding code is meant to stop at a complex node (ie one with more than two tracks) as it has no idea which should be followed. Which version are you running?

I’m afraid tuning in your situation is not yet supported.

3

I think I’m up to date:

Application: KiCad PCB Editor x64 on x64

Version: 9.0.6, release build

Libraries:
wxWidgets 3.2.8
FreeType 2.13.3
HarfBuzz 10.2.0
FontConfig 2.15.0
libcurl/8.13.0-DEV Schannel zlib/1.3.1

Platform: Windows 11 (build 26200), 64-bit edition, 64 bit, Little endian, wxMSW
OpenGL: ATI Technologies Inc., AMD Radeon ™ Graphics, 4.6.0 Compatibility Profile Context 23.19.14.08.240820

Build Info:
Date: Oct 30 2025 19:36:12
wxWidgets: 3.2.8 (wchar_t,wx containers)
Boost: 1.88.0
OCC: 7.9.1
Curl: 8.13.0-DEV
ngspice: 45.2
Compiler: Visual C++ 1944 without C++ ABI
KICAD_IPC_API=ON

Locale:
Lang: en_GB
Enc: UTF-8
Num: 1,234.5
Encoded кΩ丈: D0BACEA9E4B888 (sys), D0BACEA9E4B888 (utf8)

4

It is not supported but can be managed with the workaround: do tuning in separate steps for each branch.

  • temporarily remove the upper short segment to the central via
  • do the tuning
  • reconnect the particular short segment.
  • repeat with the other branch(es)

image
image597×733 46.9 KB

5

This is a poor arrangement, there will be a strong reflection at the fork. A daisy chained approach is better for signal integrity

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