Taking between 5 and 20 minutes before start up chime.

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?

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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.

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Hi, Thanks for the reply. It was a Mac pro5,1 12x 2.93 as it came from Apple.

www.create.pro did an upgrade on the processor board. Now it's 3.46GHz 12 Core X5690. This has been running with out a glitch for 2 years until now. I do still have the original CPU's but that's one thing I've not reverted back to for testing.

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I don't have the original board - I sent the processor board off and they updated the CPUs. I have the old CPUs but to test this I'd have to change them over which would take a while. I've run diagnostics, it froze on hardware probe once, but the second time it ran with no faults but the start up problem still persisted.

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At this point, with intermittent failures, we don't know where to look. I can't tell if you got a valid system installed on your USB stick. I don't know if you have more than one hard drive and if you have alternate operating systems on those drives. I don't know if you have the original installation optical disk. I don't know if you have another Mac to use for Target Mode. I don't know if it is infected or if you even have good virus protection.

Usually to diagnose a MacPro you try to take it back to as close to the original configuration as possible. Removing added third party RAM, PCIe cards and peripherals. Then you start up in safe mode by holding hold the Shift key in start up. Seer if you have issues.You can start in target mode with another Mac. We first have to determine if this is a hardware or software issue or a combination. If I had it in my shop, I would drop in a know good hard drive with a clean system. Run Disk Utility first and then TechTool Pro.

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Once the start up chime has happened - all seems to run well. Once OSX is running everything is fine - no KPs or other unexpected behavior. I'm concerned that the Mac sometimes takes 20 minutes before the start up chime though. This happens with no hard drives and no third party expansions at all.

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Signs of a failing power supply can include unexpected shutdowns and restarts, slow starts can be caused by a partial power supply failure. The power supply can fail on power to the drives, optical drive, PCIe boards. This can be one or several capacitors. So you can pull the PSU and examine it for bad caps (swollen and/or leaking) those can be replaced.

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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.

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