Mac Pro stuck on white screen

It sounds like the graphics card is no longer working for accelerated graphics. These cards get quite hot (the reason for the large heat sink) and do not last forever.

To use this Mac, try a replacement graphics card.

This User tip has never been updated for Mojave, but your Mac cannot run Mojave. It does lay out the issues surrounding replacing graphics cards:

User Tip: Mac Pro silver tower (2006-2012… - Apple Community

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Have you tried fixing the date? A bad date can really cause lots of problems (though I am not sure whether or not it would specifically cause this issue). You can do this by launching Terminal in your bootable Recovery Utilities system you made. I also imagine you would be able to do this by starting in Single-User Mode as well:

https://bensmann.no/changing-system-date-from-terminal-os-x-recovery

I am wondering if your install even worked properly (maybe because of the bad date it did not?). Holding down SHIFT should take you into Safe Boot Mode and not Single-User Mode (that's COMMAND-S). If you are only getting tossed into Single User command-line mode by holding SHIFT that tells me you should fix the date, erase the hard drive, and try installing again.

However, all that aside, if that isn't the issue I think the issue might be using a new 6gb/s SATA3 SSD on a machine that only supports 3gb/s SATA2 SSD. I know with 2009/2010 MacBooks of that vintage as your Mac Pro desktop that some of them barf trying to use a modern SATA3 SSD drive and require a 3G SATA2 SSD drive to use an SSD. For example, if you have a regular SATA hard drive (non-SSD) laying around I would try a test install with that and I bet that would work fine.

You could try booting up in Verbose mode (COMMAND-V) and take a photo of the last few lines of that attempt so you can see what's underneath that Apple logo where things freeze. This would shed some light on the subject, but if it's not the date... I think it's your SATA3 SSD being incompatible.

Just setting it to your current date/time is what you should do, and also make sure that it "holds" that date/time between power offs/unplug. And again, if it's still not booting I recommend a photo of the Verbose boot at the point where it gets stuck be posted here.

To be clear, did you have any problems before you did the SSD upgrade (and that's why you upgraded?) or was everything working fine and you just upgraded to the SSD for performance or space reasons?

Is it holding the date now that you fixed it that once, or does it keep on getting reset during every boot?

Have you tried unplugging everything (cards and peripherals) other than the essential devices (i.e. keyboard, mouse, GPU, ethernet). Have you upgraded any of the internal cards beyond what it came with originally?

I would try dropping the RAM to the bare minimum, aside from further reducing potential hardware issues, by simply changing the RAM (even for a single boot) and rebooting it, it will force the SMC to reset itself.

Does your model have the built-in hardware diagnostic? Try booting with the D key on power-on to see if it picks up any problems.

If all the above fails to help I would try switching any of your internal cards to use different slots to see if that helps.

I would also erase the drive again by temporarily changing the partition type to MBR & FAT32, making sure it makes the change, and then going back to change it to GUID & HFS+. By temporarily changing it in this fashion that will clear out some low-level boot sector info in a way that simply erasing it won't.

If this still fails my last idea would be to use an external USB drive enclosure or drive dock with your drive and seeing if you are able to reinstall and run OS X strictly off the external as a test to eliminate any internal SATA issues.

I don't know about the test LED behavior for the Mac Pro, I'm afraid. I just know that changing the RAM total does force some house-cleaning by the system, resetting the BIOS a bit, which is a good thing and can clear up problems.

Since there was this whole issue though before you even upgraded (thanks for clarifying that) it makes me concerned that there is some low-level hardware issue going on, and if none of these minor tricks kick it into working then that's the conclusion.

Definitely give the external drive technique a test. Also, during the OS X installation you can bring up the log during install I believe. You should see if there's anything enlightening there or not.

One last thing, looking at your Verbose screenshots I do see there was an SMC-related error, however one cannot automatically jump to the conclusion it means there is an SMC related problem or not. Some errors are "normal", and unfortunately I don't have enough base-line experience on these older Mac Pros to say for sure. But between changing the RAM total, and replacing the CR2032 battery, that's about all you can do in terms of SMC troubleshooting other than looking up any error codes that the Diagnostic mode test reveals.

But minus this last bit of testing (external drive-installed OS and Diagnostics mode) and depending on the results, that's about all I have for you!

Good luck!

The RAM was marked as OK by the system info, but when I made the boot a red LED series flash for a second on RAM’s board. Is it normal?

That is behaving as designed.

Hardware turns the LEDs on, and after it passes the Power on Self Test, software turns off the ones that pass. Any left on are BAD.

<<AHT (Apple Hardware Test) not available with 10.7.5, so I can't perform it.>>

Apple Hardware Test (AHT) for that Mac was shipped on the original-issue DVDs specific to that model. I do not know of ANY Mac that shipped with a 10.7 DVD.

The diagnostic was also installed on the ORIGINAL drive, but no software was responsible for replacing it after drive erasure or drive-swapping, so in most cases Apple Hardware Test on the Boot drive has been lost.

One enterprising user has collected all the easily-found copies of Apple Hardware Test on a Github site, and included a procedure for making a stand-alone Apple Hardware Test USB-stick:

https://github.com/upekkha/AppleHardwareTest

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