Dark blue monitor screen using 2012 Mac Pro Tower

Hi, keith358, my bet’s on a video/graphics card that has, or is about to, fail, you should also replace the CMOS/PRAM battery as well, which is behind the video/graphics card in the backplane… the battery is officially a BR-2032 but a CR-2032 will work fine, goes in ( + ) plus side up..,costs you about $5, as for video card, Radeon HD 7950 should do fine for starters.., either Mac native or Mac flashed will work fine in a Mac Pro 5,1… I bought a Mac flashed one from eBay, $300 CDN shipping included, and it has 6 GB of vram, not too shabby there…

John B

Vertical artifacts are almost always limited to the display itself, not graphics cards or any other component. That the display passed a test with another computer suggests the problem was transient in nature.

Vertical artifacts are almost always display issues, because the pictures they display are a stack of display rows, exactly the same length, each drawn below the last. As long as the display RAM, rasterizer/display generator and cable are all working properly, that will enable the display of vertical lines. The moment anything screws up, the rows will no longer be the same length, and Vertical lines will no longer be vertical.

it is only inside the display itself where everything drawn into Mac memory comes back around to be displayed as a vertical line.

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The litmus test for whether the display is in error (and therefore the graphics processor made this mess) is to grab a screenshot. A screenshot is made by copying what is in display RAM. If the screenshot has no artifacts, but the display has artifacts, the problem is in the display.

A continuous startup chime can give some basic clues.

see > If your Mac beeps during startup - Apple Support

To try for some better clues, see if it will run the Apple Hardware Test.

see > How to use Apple Hardware Test on your Mac - Apple Support

Hi,

If the start up chime is ring, I think your video card is failure.