u/Intrepid-Bother2440

Dell WD25TB5 (TB5 dock) achieving dual 4K144Hz on MacBook M1 Pro (TB4) - undocumented

I stumbled across this by accident and can’t find it documented anywhere.

Setup:

•	MacBook Pro M1 Pro (Thunderbolt 4)

•	Dell WD25TB5 Thunderbolt 5 dock

•	Dough Spectrum One and Dell G3223Q (both 4K 144Hz)

The trick:

•	Dock’s DP output → Dell G3223Q

•	Dock’s TB5 downstream port + USB-C to DP cable → Dough Spectrum One

macOS sees both as independent display streams rather than MST (which macOS doesn’t support), and both hit 4K144 — presumably via DSC compression fitting within the TB4 bandwidth.

Comparison: Same MacBook on a Plugable TBT-UDT3 TB5 dock only gave 4K144 + 4K60. The Dell dock is clearly handling DSC negotiation better internally.

M1 Pro natively supports two external displays so no DisplayLink needed — just the right cable configuration.

Has anyone else achieved this?