A Mac Pro 3,1 is misbehaving...

[howiest]

I’m helping a friend with his 2008 Mac Pro 3,1 Octo. While troubleshooting some email issues, I noticed that only 2 GB of RAM were registering in System Report. Which explains how sluggish his computer is.

He has 6x1 GB DIMM's installed but only 2 are reporting. I reseated the DIMMs and exchanged the risers, with no luck.

No matter what config I did, only 2 GB showed up.

When I have a chance to get back I plan on running Apple Hardware Test, and reseating the RAM again. I’ll also do a NVRAM reset and an SMC reset. Beyond that, I’m concerned that his logic board is dying. Because there's no way that 4 DIMMs would die all at once.

Any thoughts are appreciated.

 

[pl1984]

Is this a dual processor system? Perhaps one of the processors has failed resulting in its memory not being available? How are the DIMMs allocated on the riser cards?

 

[OS6-OSX]

 

[howiest]

The 6 DIMMs are installed as shown in that ^^ picture.
The weird thing is that I reversed the riser cards, and changed the DIMM config, and no matter what I did only 2 GB reported. 10 year old computer, so not really all that surprised, but ...

 

[haralds]

Are there any red lights indicating failure. One of our systems lost 2 4GB DIMMS for some reason. They were 3rd party with lifetime warranty, which was honored.

 

[howiest]

Are there any red lights indicating failure. One of our systems lost 2 4GB DIMMS for some reason. They were 3rd party with lifetime warranty, which was honored.

I'll check for lights when I have another look at his machine.
I just can't imagine 4 1GB DIMMs all failing at the same time. But it is possible I guess.

 

[pl1984]

The 6 DIMMs are installed as shown in that ^^ picture.
The weird thing is that I reversed the riser cards, and changed the DIMM config, and no matter what I did only 2 GB reported. 10 year old computer, so not really all that surprised, but ...

Specifically how did you change the riser cards and DIMM configuration? Was there ever a configuration where you had four DIMMs in the lower riser? Have you attempted to test all of the DIMMs by using a two DIMM configuration to ensure you have 2GB for each pair?

 

[tsialex]

I'll check for lights when I have another look at his machine.
I just can't imagine 4 1GB DIMMs all failing at the same time. But it is possible I guess.

Yes, it's possible and happened with me. FB-DIMM works hot and after all this years, they fail.

I had to test one by one with Memtest86 to separate the good ones from the bad ones. Some didn't lit the error led but Memtest86 showed hundred of errors.

 

[yuzgen]

I bet there's nothing wrong with the Mac Pro. If one of the RAM pairs fail, the other one will not be used.

Try changing pairs, ie find a good match

If it fails, try your good pair of RAM sticks in different slots, no other RAM installed, just the working pair in different slots. You'll most probably see they work.

 

[howiest]

I bet there's nothing wrong with the Mac Pro. If one of the RAM pairs fail, the other one will not be used.

Try changing pairs, ie find a good match

If it fails, try your good pair of RAM sticks in different slots, no other RAM installed, just the working pair in different slots. You'll most probably see they work.

Good advice. One pair was added after the machine was purchased, and if they are bad, they have a lifetime warranty. Once I get access to his machine again I'll narrow it all down.