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macrumors newbie
Original poster
Sep 9, 2019
Hi, I just bought a Mac Pro 5.1. Single Processor Xeon 2.8 Ghz and ATI Radeon HD 5770. The computer came with Snow Leopard installed so my next step was to begin the upgrade process to at least High Sierra until I buy a Metal compatible GPU.
The problem I came up with was that I foolishly installed a few updates to that Snow Leopard HDD. Something to note was that the display was set to 1024x768 and I was unable to increase the resolution. The machine rebooted and after that it only displays the boot screen and then the display brings a "Cable not connected" sign. The display is a VGA 15 inch 1280 x 768 (New one coming soon, I know) and connected to the 5770 via an adapter on the DVI port.
My attempts to solve the issue (which I think they might surely be from a faulty video card or -less likely- a faulty PSU) were the following with what I have in hand:

- Reset SMC and PRAM
- Try to boot a High Sierra Installer on a USB Stick (no luck), still no video after boot screen
- Try to boot earlier MacOS installers, no luck
- Change the 5770 to a different PCIe Slot, no luck
- Switch the GPUs power connector to PCIe 2, no luck
- The computer seems to boot bout I have very little tools at my disposal
- Diagnostic lets seem to be alright
- Searched all across the web for solutions but count find this issue

Any Suggestions? Thanks
Last edited:


macrumors newbie
Original poster
Sep 9, 2019
Thanks a lot h9826790!
The problem is in the DVI to VGA adapter!
I just purchased a Mini DisplayPort to VGA and it works.
Thanks again!
Time to get started with my new machine!
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macrumors 6502
Apr 11, 2018
Wondering about your adapters, is the DVI to VGA passive and the Mini DisplayPort to VGA active?
That could explain why one works, and the other doesn't I think
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