Windows RDP (Remote Desktop) can I force to disregard GPU?

RDP before Windows 10 had its own graphics driver to convert the rendered screen into network packets to send to the client, which used exclusively the CPU. Window 8 was the first to start using the GPU.

Since Windows 10 build 1511 and Windows Server 2016, RDP uses the AVC/H.264 codec in order to support larger screens than full HD. This codec uses the GPU, but only under certain conditions and for full desktop sessions, but otherwise falls back to using the CPU as before.

Using AVC/H.264 is now the default, but you may disable it using the Group Policy Editor (gpedit.msc) and drilling down to :
Computer Configuration -> Administrative Templates -> Windows Components -> Remote Desktop Services -> Remote Desktop Session Host -> Remote Session Environment.

Set the following policies to Disabled, to disable the use of the AVC/H.264 codec :

• Configure H.264/AVC hardware encoding for Remote Desktop connections
• Prioritize H.264/AVC 444 Graphics mode for Remote Desktop connections

In any case, non-full desktop sessions should not currently use the GPU (but this could change without notice).

References :

• Remote Desktop Protocol (RDP) 10 AVC/H.264 improvements in Windows 10 and Windows Server 2016 Technical Preview

• Configure H.264/AVC hardware encoding for Remote Desktop Connections

The last reference contains this text :

This policy setting lets you enable H.264/AVC hardware encoding support for Remote Desktop Connections. When you enable hardware encoding, if an error occurs, we will attempt to use software encoding. If you disable or do not configure this policy, we will always use software encoding.