So I have a Mac Pro 4,1 which I flashed and upgraded to 5,1 with dual X5680s and for the longest time I have been having a really annoying issue. I mainly use the machine in Windows 10 and when the machine is just sat idle, like watching a YouTube video, using chrome or just basic apps it will just hang, display a black screen (with a signal, not turn the monitor off) and all activity will cease until I hold down the power button and restart. Interestingly it doesn't seem to happen if the machine is under load, such as gaming. Has anyone experienced anything like this before? Any ideas on how to fix it as it's really annoying. The specs of the machine are as follows: Dual Xeon X5680s 24GB (8GB x3) Samsung ECC 1600MHz Memory (running at 1333MHz) ASUS Strix AMD Radeon R9 390 8GB HyperX Savage 480GB SSD 2x Hard Drives (SMART OK) Original Nvidia GT120 (For boot options) 4 Port Fresco USB 3.0 Card Sata III Card (For boot SSD) This also only seems to occur in Windows, and I have installed and reinstalled it several times including bootcamp and EFI methods, currently running EFI. Any help would be appreciated.