I have replaced the ATI Radeon HD 5770 that came with my early 2009 Mac Pro (flashed to 5.1) with a MSI Radeon RX 560 Aero ITX which is compatible with Mojave.
Since the new card doesn't provide a mini Display Port port, I uses a miniDP to DP adapter in order to connect my Led Cinema Display monitor.
Unfortunately the "Led Cinema Display" sound option does not appear anymore in the sound panel of System Preferences. Therefore I have to use the USB channel instead. Unfortunately with this channel the sound is delayed about half a second from the event that triggers it, such a mouse click.
Is that due to the new graphic card or may be to the adapter ?
Any clue ?
Thanks bookemdano, however, the link you provided is about using the HDMI port not the Display Port. Is there a similar way to effectively use the DP ?
Also, what do you mean by "third party" cards. Do you mean those cards that do not have the Apple Rom, that is those that don't have Boot screen ?
@BBA43 though there is clearly a difference between HDMI and Display Port and their protocols, in this case the link provided with a generalization of "HDMI Audio" does mean both HDMI and Display Port, as well as Mini Display Port should you have a GPU with mDP also. Meaning the link provided will get you audio out your DP output, HDMI output, and mDP output, granted that you have those outputs available on your installed GPU.
3rd party cards basically mean any GPU not considered a "mac edition" GPU which is basically all PC GPUs that do not have the EFI version to run more seamless with Apple's systems. Even shorter version is if it wasn't available as an offical BTO option when the Mac Pro was bought/built, its considered 3rd party. For example, though not a "mac edition" GPU, Apple is recommending and supporting Sapphires Pulse RX580 8GB GPU for use with Mojave. This GPU doesn't have EFI, isn't made by Apple, but they do support it on their system. This HDMI/DP/mDP audio hack is still needed for that card too despite it's support
