Triple Monitors on Mojave OOTB - Success

[rwillett]

Hi,

I know a number of people have had issues with dual and triple monitors on Mojave with 280X graphics cards.

I managed to get mine to work and so I thought I'd detail what I did.

My original installation had Sierra (not High Sierra) with dual 280X Sapphire Vapor cards. I had three monitors all driven through DVI connectors out of the box across the two graphics cards. This worked very well under Sierra but I could not get the same configuration working out of the box with High Sierra or Mojave.

I tried a number of different threads detailing changing the framebuffer and writing various codes out to the config.plist file. None worked for me with the DVI ports. I kept building and rebuilding and reinstalling and didn't get anywhere.

I tried various DVI to VGA active connectors as one of the monitors goes to a four way KVM. Again nothing.

What did work was moving off DVI onto Display Port and to HDMI. Two of my monitors have Display Port and the third monitor has VGA and HDMI but nor Display Port. The monitors are a little odd

Anyway, I plugged a Display Port to VGA adaptor in to the 280X, connected one monitor back to my VGA KVM, plugged a DP to DP adaptor in for the second monitor and used the HDMI connector on the 3rd monitor.

Reinstalled again and it 'just worked'. No framebuffer changes, no clever config.plist. Standard Mojave install for UEFI.

Rob

 

[trs96]

Good to hear that your R9 280X cards are still getting the job done in Mojave. The simple fixes are the best IMO.

 

[rwillett]

Agreed.

Since the 280X cards still work well, it's a shame to just discard them, especially as I have two of them.

It does appear that the Sapphire 280X cards are very 'reference like' as I have not had to do any framebuffer changes ever to get them to work. Since I use my Mac for work, I don't need the latest nVidia monster for PC gaming.