請檢查你的DP線材是否是通過認證的線材。
不是的話請拿電表量一下pin 20有沒有導通，有的話就是因為現材沒有照標準設計，DP_PWR 3.3V有接上，導致螢幕端無故回灌了0.5A的電流造成主機板端的誤動作。
由於螢幕跟顯示卡兩端都會對DP_PWR供電，除非是針對特殊裝置使用的特殊情況，否則那根針腳應該不可接上。

詳請請見Displayport.org的FAQ:
Q: Why isn’t there a wire on pin 20 (POWER) on the standard external DisplayPort cables?

A: The reason power isn’t included in standard cables is because both source and sink devices are designed to provide power. Captive, attached cables often include the power wire. If it is desired, for example, that a particular source device utilize the power available from the mating sink device, then that Source device could include an attached or dedicated cable that carries the DisplayPort power signal. Same could be applied to a sink device.
http://www.displayport.org/faq/