MP 1,1-5,1 RX580 multiscreen support question

[idealtracks]

I have a 5,1 MacPro, running Mojave, currently with an r9 280x GPU, but I'd like to upgrade to an RX580 and use it with 5 displays (a 4k monitor, 2x 1080p monitors, and 2x 1080p vertical monitors, if that matters. Having access to the Boot screen is not important as I have other cards to use in a pinch.

Will a standard Sapphire Pulse RX580 PC card push 5 displays out-of-the-box, or would I need to buy an expensive modded one with a custom Mac EFI to be sure this 5-display feature would work? I just want to be sure before purchasing. Thank you!

 

[minifridge1138]

The only modded firmware I know of for the RX 580 is the MVC mode to get boot screens and that doesn't offer a performance boost to help you drive more displays.

 

[mattspace]

My experience with the Pulse RX580 and 3 displays is that it's not perfect. Part of this could be the displays - my main display on DP1.4 or 1.1 takes a lot longer to wake up than the other two on HDMI (or as they were on DP). Occasionally during wake, one of the HDMI displays will disconnect and reconnect, shifting all its content for *some* apps over to the middle screen.

In recovery mode, nothing will show on any screen, until the main screen is toggled from DP 1.4 to 1.1, and then recovery appears on an HDMI screen (which is problematic, as it's rotated 90 degrees).

Assuming the problem isn't the monitors, I wouldn't put it past Apple to have only tested the drivers for this card with 2 displays total.

 

[iGobbleoff]

I was in a similar boat before with my 5,1

I had an MSI RX580 and it was driving 3 4K screens and most of the time it was ok but once in a while one screen wouldn’t wake from sleep until I reboot it.

 

[mattspace]

a 4k monitor, 2x 1080p monitors, and 2x 1080p vertical monitors, if that matter

Just be aware if you haven't used unmatched displays before, that with different displays of different PPI, objects are not going to be the same size, so a document or window spanned across them won't match up.

A solution to this is to use SwitchResX to create virtual resolutions for your lower dpi screens - eg I have a 109ppi 2560x1440p main screen, and 94ppi 1920x1200p secondary screens. I give them virtual resolutions of 2226x1390, and everything matches up perfectly across screens.

 

[idealtracks]

Great advice all, thank you very much. I've just ordered a card and will follow up with my experience after it comes in.

 

[mattspace]

Great advice all, thank you very much. I've just ordered a card and will follow up with my experience after it comes in.

Another quirk - DVI won't do 10 bit colour, and the HDMI ports are physically bound to where you place them in virtual space - the HDMI port next to the DP port has to be plugged into the monitor on the right of the other hdmi montor, otherwise you get all sorts of weirdness in the monitors prefpane if you set rotation on them.

also that binding can flip in different major macOS versions.

 

[idealtracks]

Just to update, I got the Sapphire Pulse RX580 PC card today. I had no problem hooking up 4 monitors so far. No problems waking from sleep. I've got the 4k 50" via HDMI, 1x 23" dvi via HDMI to dvi adapter, 2x vertical 23" via DP converters. I had forgotten that one of my 23" monitors has a dead DVI input so I'd been using it via VGA for a few years. I'm ordering an active DP to VGA adapter... we'll see how that goes...
Update: I got the Startech DP2VGA2 adapter, and all five screens are now working fine. This is the best video card I've ever owned!