The racing fan bug is a well known issue that affects a certain percentage cMP systems with upgraded video cards. On these systems the PCI, PS, and booster fans spin abnormally fast at idle, causing unnecessary noise and vibration. Although the issue appears to be connected to PCI power draw and the SMC, the exact cause remains unknown. With many users upgrading their video card for Metal, this bug is undoubtedly claiming more and more victims. A popular solution to this bug is to use fan control software. The advantage of this approach is that profiles can be created that not only calm the fans down but also keep systems with high-power components running cool. Another solution is to restore the native fan control by stressing the GPU. This approach causes the fans to rev up for a few seconds and then calm down to stock speeds (staying calm through sleep cycles and reboots). Because it restores the native fan control and is quickly out of the way, some users prefer this approach. However, this approach lacks the automation of the first. Users must find appropriate software (a benchmarking app or a game) and run it for some time. Introducing AirOut: a simple fan-triggered GPU stressor. AirOut is a small Metal app that stresses the GPU seamlessly in the background if it detects high fan speeds. The app immediately quits after issuing the stress test. It also offers a forced mode, which stresses the GPU regardless of fan speed. To enter this mode, simply start the app while holding down Command. The app uses notifications. The alert style can be set in System Preferences > Notifications. (With banners, user interaction is possible by hovering the mouse pointer over the notification.) To have the app run on startup go to System Preferences > Users & Groups > Login Items. There, add the app to the list of items. New in version 1.0.1: In some cases, a delay after login is required to properly reset the fans. By default, the delay is 0. To add a 60 second delay, for example, enter the following in terminal: Code: defaults write com.airoutteam.AirOut DelayAtLogin 60 This setting only affects the app when it runs as a login item. To reset it, simply enter this: Code: defaults delete com.airoutteam.AirOut System requirements: AirOut runs an intensive computation (about 2 gigabytes worth of a matrix multiplication). It requires at least 2 GB of RAM. Because the racing fan bug varies depending on the video card (which seems to affect the amount of stress required to reset the native fan control), AirOut will currently only run on the popular 8 GB RX 580 video card. AirOut will also only run a Mac Pro 5,1 (including, of course, a 4,1>5,1). Warning: AirOut is still considered experimental. Even if these requirements are met, it is not guaranteed that the native fan control with be restored (or even that your system will not explode ). Please comment on how the app works for you here!