Hi Folks, I have a Mac Pro 5,1 running High Sierra v10.13.3. Recently, I installed a new Sapphire Radeon RX580 GPU as detailed here... LINK ...super thanks to the guys that advised on that thread! I finally got the cables and installed the card and everything is up and running, but seem to be having this weird issue. Normally, I would have reported there, but I'm not so sure it's related. Here's the deal... the system works great with the following exceptions... - If I leave for a while (long enough for the display to go to sleep) when I return, nothing seems to work to get the computer to wake up. The beacon light is "breathing" as if it's sleeping, but pressing it doesn't wake-up the system. Shaking my Bluetooth Might Mouse does nothing. Pressing buttons on the keyboard does nothing. My only option is to hold down the power button until the system shutsdown and then reboot. - My boot time is markedly longer now. I'm using a Samsung SSD 840 EVO 250GB that currently has 70GB available. Prior to my GPU "upgrade" boot time of the system was less than 30-seconds; now it's north of a minute. - Simple things like moving or copying files between folders or between hard drives... Saving files as PDFs (ie: printing or exporting) files smaller than 100kB... what used to be virtually instantaneous seems to take 30 seconds now. This is the same regardless of application... I've been using MS Word; Excel; Preview; GIMP... same story. Plenty of RAM available... 8GB Free out of 16GB. I'm running a 6-core 3.33Ghz Xeon processor. Any insights? Thank you! Paras.