Chosen Solution
When it’s running - everything seems fine, but my Mac Pro takes an age to do the self test, sometimes it doesn’t start at all after 10 - 15 minutes. Sometimes there will be a long wait - followed by the case fan ramping up to full RPM (alarming) then the start up chime and a normal boot. I’ve stripped the mac down removing all third party bits, replaced updated graphics card with the original, tried the stock ram (completely different set), disconnected all hard drives and PCIe cards. I made an apple hardware diagnostics USB stick for this model. It froze a couple of times on the initial hardware probe but passed with no errors twice, but the start up issue still persists. I restored the upgraded RAM, GPU, SSD etc, and the behaviour didn’t change, however AHD did pick up on a PCIe temp sensor error - on researching this it seems this is a false lead and simply due to my third party GPU sending back unexpected readings. Other people with the same GPU get the same error and their systems are fine. Done NV Ram reset, SMC reset, Logic board battery replacment. So I’ve got a Mac Pro that can take 10 minutes plus to get to the point where there’s a start up chime, but once it’s running, there appears to be no issues. It makes me nervous though because there is obviously some issue there, probably with the firmware or hardware and I find it difficult to get on with work knowing that there’s a problem which may start manifesting in other ways. I had the CPU’s upgraded to 2 x 6 core 3.46. Originally this machine was 2 x 6 core 2.93. Has anyone got any ideas?
Tell us more about this “third party CPU upgrade”, please. UPDATE That’s the first thing I would look at (what has been altered). It sounds like you do have the original board. It takes less than a minute to slide to old one into place, just flip the two levers and slide it out and slide the old one back in. I would unplug it before doing this. If you still are having problems, boot up from the original system installation disk holding down the D key and run diagnostics on it.
Fixed it!!! The answer was corrupt firmware. The apple firmware recovery tool (intended to rescue bricked machines due to firmware flashing failure) ended up fixing it. Never seen anything like this on a Mac before.
@stuartfox thank you so much, I didn’t even know Apple provided a means to restore firmware from CD. I had exactly the same issue with my 4,1 flashed as a 5,1 taking minutes to get a boot chime (fans going to take off mode and sometimes never booting, then once reaching the chime no other issues in OSX). For the benefit of anyone viewing this later, I was running a non-EFI GPU so I had to re-install the old GT 120 I kept in the loft to apply the process described here: https://support.apple.com/kb/dl1320?loca… One thing I’m not sure about is the firmware version the above link will restore? Firmware updates are important for anyone who is running High Sierra or Mojave (the latest one being 144.0.0.0) but I can’t tell what version this CD applied. It doesn’t matter for me as I’m using OpenCore Legacy Patcher to boot Big Sur so the firmware version shows as 999.999.999.999. If you are running Mojave or High Siera natively, you might need a old version of OSX available to boot up and re-run the above installers to re-apply the firmware updates.
