Two Mac Pros now freezing

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Two Mac Pros now freezing

Hi - I'd be grateful for help. I have two Mac Pros, one running Snow Leopard 10.6.8 and one running Lion 10.7.5

Sophos and Memtest give both machines the 'all clear'.

The Snow Leopard machine recently began to freeze after startup. As it's an old OS, the Genius Bar people couldn't really help much, but suggested a hard drive problem. Other people I consulted agreed.

I replaced the HDD and restored using Time Machine, but got the same problem: freezing after startup. I restored again, this time to a much earlier point, without curing the problem.

I then did a clean install of Snow Leopard, but the problem persisted, so I removed the drive and put it in my other Mac Pro, erased it and did another clean install of Snow Leopard. The same problem occurred on this machine: freezing after startup.

Such tests that I can run on the new drive indicate no problems. Incidentally, after the fresh install of Snow Leopard, both machines freeze in safe mode and during Apple Hardware tests.

After removing the HDD the Lion machine ran perfectly well again. The only conclusion I can come to is that the new HDD is not working properly, but it seems unlikely, especially as it shows exactly the same symptoms as the drive it replaced.

I don't mind admitting I'm stumped. All suggestions will be greatly appreciated!

Mac Pro

Posted on Jul 17, 2015 9:47 AM

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Answer 1

Drew Reece

Level 6

10,684 points

Jul 17, 2015 10:25 AM in response to Pjrcomposer

Have you removed all third party addons? Disconnect all non-Apple peripherals too.

If hardware test & a clean install is failing it indicates a serious error with the hardware.

You can try removing the memory modules to see if they are part of the issue. If you have been swapping them double check they are seated correctly & in the correct sockets for the model, the side panel usually has instructions printed or you can get the correct manual for your model(s).

Apple - Support - Manuals

Verbose mode may give you more detail when the freeze happens…

Mac OS X: How to start up in single-user or verbose mode - Apple Support

You may want to track down the spec for the model, just to be sue that it supports whatever type of HD you brought, There is a slim chance that a new SATA standard is not fully compatible, but it seems unlikely. To rule it out I'd remove all HD's & try installing & booting from an external OS X installation. USB can work, Thunderbolt & Firewire will be quicker.

P.S. Take care to keep each OS installation labeled for each model. Sometimes one model will not boot from an OS created on another model.

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Answer 2

Pjrcomposer Author

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Jul 17, 2015 10:39 AM in response to Drew Reece

Thanks Drew for taking the time to reply. I should have mentioned that I'd disconnected all non-Apple peripherals and third party add-ons.

I also originally assumed the Snow Leopard machine had developed a serious hardware fault, but when I formatted the new drive in my other machine and did another clean install of Snow Leopard only to have exactly the same problems, I began to assume the issue lay elsewhere.

I will certainly check the SATA standard - that's a great idea, thank you. I'm no technical whizz, unfortunately, so I appreciate your help.

Thanks again!

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Answer 3

Drew Reece

Level 6

10,684 points

Jul 17, 2015 12:53 PM in response to Pjrcomposer

Are you using the original OS install disk for Apple Hardware Test?

They are model specific & that could explain why that freezes if they are the incorrect version. The grey OS disks have the version printed on them.

There is a list of AHT versions & downloads at…

https://github.com/upekkha/AppleHardwareTest

They can be burned to CD (or written to a bootable USB stick) to use for ruling out your current AHT disk as the fault.

I made a script to write AHT to a USB stick…

https://gist.github.com/drewreece/2e5eed7dbfbd5dd7e929

Ask if you want to try that, but it's a longshot in all honesty.

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Answer 4

Pjrcomposer Author

Level 1

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Jul 17, 2015 1:58 PM in response to Drew Reece

I used the original grey disc for the Snow Leopard machine; I no longer have the original discs for the Lion machine. I wasn't aware of the link you provided, so that's incredibly useful; I'll download the appropriate tests tomorrow. I'm probably going to exchange the new hard drive; aside from the Snow Leopard install disc that's the only thing the two machines shared and they were showing the same symptoms.

Thanks again for your help and advice; I was beginning to despair! 🙂

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Answer 5

Jul 17, 2015 7:07 PM in response to Pjrcomposer

Are you getting kernel panics? that are saved in a log described in this article:

Mac OS X: How to log a kernel panic - Apple Support

If you are, cut and paste the text to a reply on the forums and readers can help you make sense of them.

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