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FW13 AMD 7040 standalone: no DisplayPort Alt Mode output on a port that is simultaneously sinking USB-PD (single-cable monitor operation impossible) #258

Description

@Ekstraktly

System Model or SKU

Framework Laptop 13 (AMD Ryzen™ 7040 Series)

BIOS Version

3.20

DIY Edition Information

Port/Peripheral Information

No response

Standalone Operation

Mainboard only, Standalone mode enabled

Describe the Bug

On a standalone 7040 mainboard with no main battery, a USB-C port will not output DisplayPort Alt Mode video while that same port is acting as a USB-PD sink. The board accepts power from the monitor and boots normally, but no video signal is ever produced.

Adding a second, independent USB-C power source on another port makes video appear immediately over the same monitor cable, with no other change. The only variable is whether the monitor's port is also the power source.

Monitor is an HP Series 7 Pro 727pk, whose Thunderbolt 4 upstream port is rated for 100W. The board boots and runs on this monitor's power alone, so the power path is not the limitation -only the video path is.

Tested on all four USB-C receptacles with no expansion cards installed, so this is not an expansion card or port-slot issue. (Noting for completeness that the front-right receptacle is USB 3.2 only and not expected to carry video regardless.)

This makes single-cable operation impossible on a standalone mainboard, which is the primary use case for the Cooler Master Mainboard Case.

Steps To Reproduce

  1. Standalone 7040 mainboard, no main battery, Standalone Mode enabled, BIOS 3.20, no expansion cards installed.
  2. Connect only the monitor's USB-C cable directly to a mainboard receptacle.
  3. Press the onboard power button. Board powers on and boots. Monitor receives no signal.
  4. With the board running, attach a separate USB-C charger to another receptacle. Video appears on the monitor over the existing cable within seconds.
  5. Remove the separate charger. Board powers off immediately (expected with no battery present).
  6. Repeat steps 2–5 on each of the four receptacles. Identical result on every port that supports video.

Expected Behavior

A single USB-C cable from a PD-capable monitor should supply power to the mainboard and carry DP Alt Mode video out from it, as it does when the same mainboard is installed in a laptop chassis with a battery, and as it does with other USB-C mini-PCs on the same monitor.

Screenshots

No response

Operating System

Windows 11

Linux Kernel Version

No response

Additional Context

This appears to be the same class of problem as EmbeddedController issue #43, "No graphics when requiring both power delivery and video output," which was closed with no comments and no fix. It also matches the community report "Standalone Framework 7840U Board Limitations," where all four ports were tested with the same outcome, and where Framework support reportedly stated the 7840U was never designed for this configuration. Behavior persists on BIOS 3.20, which included a fix for a monitor-related black screen issue.

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