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I have two mirror drivers showing up in Device Manager (in Windows), from RealVNC and UltraVNC. What exactly does a mirror/hook display driver (adapter?) do?

I'm curious about the actual mechanism(s) of functionality, and why a regular display driver/adapter doesn't suffice.

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up vote 1 down vote accepted

Based on this description, it's simply a virtual driver that mirrors the operation of a physical device. It's basically installed as a driver for a virtual graphics card. This means it gets immediate notification of all display updates, allowing the VNC server to react quicker and use less CPU. A regular display adapter doesn't suffice because you aren't interacting with hardware (a monitor) the same was as if it were plugged in normally.

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Thanks! Much obliged. – Coldblackice Jun 28 '13 at 5:28

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