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Displayport brain-buster

Last response: in Systems
April 2, 2011 2:12:29 PM


I can't figure this out:

While my PC is OFF, the Power Supply's fan (Corsair TX 750w) will spin intermittently, pulsing on for a moment once every second.

It only happens when my Video Card (ATI FirePro v7750) is connected to a 27" iMac that I use as my PC's Monitor.

The PC and iMac are connected via a mini DisplayPort to DisplayPort adapter and a DisplayPort cable.

If I disconnect the monitor/iMac, then the intermittent fan spinning stops.


a c 90 B Homebuilt system
April 2, 2011 3:46:08 PM

Hello keats;

That is odd. And probably deserves the topic title you picked.
Is the iMac display completely powered down or in standby mode?

Try disconnecting the display from the AC wall socket and see if you get the same symptoms.
April 2, 2011 8:18:14 PM

Hi WR2,

Thanks for the reply.

The symptoms occur so long as the iMac is both on, and plugged into the PC's display card. If I put the iMac to sleep or shut it down, the PC's PSU fan stops all spinning.

My pure speculation is that the iMac is sending some sort of signal out via the mini DisplayPort once per second, to detect whether a device is connected to it or not, because normally it will detect when the PC is on and engage Target Display Mode. And maybe that signal is interfering with the PSU fan.

FYI motherboard is ASUS P6TD deluxe.

a c 90 B Homebuilt system
April 2, 2011 8:21:33 PM

Is that the all-in-one 27" iMac?
I wonder if it's some type of network polling signal.