HD 6870 in Mac Pro isn't showing the 2560x1080 resolution.
HD 6870 in Mac Pro isn't showing the 2560x1080 resolution.
I bought a Mac Pro 1,1 and installed El Capitan. I also got two HD 6870 graphics cards to ensure smooth performance. I usually get 1080p, but with 2560x1080 (LG Widescreen) it looks like only half of it centered on my screen. I've tried various adapters—Mini Display Port, HDMI DVI, and even an adapter to a real HDMI cable—but nothing seems to work. I wonder if the cables I'm using are compatible with 2560x1080 resolution. Need some advice!
OS compatibility issues arise because AMD and Intel drivers are built into OSX/MacOS. Full HD performance requires a HDMI 1.3 or higher direct connection; otherwise, you must use HDMI as the input source without adapters.
Regarding the Mini Display Port, it appears to function differently from the others. Instead of compressing the image, it doesn't display 2560 at all. Using SwitchResX didn't produce the expected results, which led to reinstalling El Capitan. This suggests the cable likely reached at least 2560x1080 resolution, but your monitor couldn't handle it. You might want to try different settings or configurations, or consider alternative solutions if troubleshooting proves difficult.
I've dealt with this before—on my Hackintosh laptop, the output to my Ultrawide screen using DP isn't working, only HDMI. It seems DP gets messed up with the right adapters. Maybe using a different USB adapter or checking for an AMD card with HDMI would help.