Mac Pro 2008 - RAM modules dead

sparkie7

macrumors 68020
Original poster
Oct 17, 2008
2,037
106
Had very little sleep last night as my Mac Pro wouldn't start up on switching start up drives. Blinking white light. Never seen this before. Wouldn't even allow the keyboard to work so I couldn't reset PRAM, or make it a target disk.

Open up and saw red flashing coming from RAM slot bay area.

After a lot of swapping out the 4x 4GB RAM modules I isolated that TWO of the modules were not working. Surprised, as I only expected one bad one. But not two!

Anyway, pretty sure these are covered under Ramcity's lifetime warranty. Will contact them to get these returned for replacements. Hopefully no issues with them..

Anyone else had 2x modules die on their Mac Pro, do they often die in pairs?
 

netkas

macrumors 65816
Oct 2, 2007
1,134
313
I've had another issue with ram on macpro. Might be related.

I've expirienced my MP to randomly shutdown, had 8 memory sticks, 4x1gb and 4x2gb. played a lot with sticks configuration, suspected 2 2gb sticks in failing.

After lots of test I've came to conclusion that all 2gb sticks could be failing.

Having only 4 1gb sticks MP was stable.

Ordered 4x4gb sticks.

Installed 4x4gb stick to macpro (total 16 gb ram) - works stable

added 4x1gb sticks (total 8 sticks, 20 gb) - randomly shuts down o_O

I've came to conclusion it only works stable for me if only 4 memory sticks are used (2 on upper riser, 2 on buttom)
 

sparkie7

macrumors 68020
Original poster
Oct 17, 2008
2,037
106
I've never tried mixing RAM amounts.

I have had the 4x 4GB sticks in for almost 5-6 years without a glitch. They are identical and from the same manufacturer etc..

My understanding is as long as they are MATCHED PAIRS they should work. Even if you install your 4x 1GB modules. Have you tested whether some of your 1GB Dimms maybe defective?
 

netkas

macrumors 65816
Oct 2, 2007
1,134
313
I've never tried mixing RAM amounts.

I have had the 4x 4GB sticks in for almost 5-6 years without a glitch. They are identical and from the same manufacturer etc..

My understanding is as long as they are MATCHED PAIRS they should work. Even if you install your 4x 1GB modules. Have you tested whether some of your 1GB Dimms maybe defective?
1gb moduels are fine.

in fact 4x1 + 4x2 worked well for an year.

My guess was - a problem with riser cards or system logic board. Didn't care much since 4x4gb is working well
 

sparkie7

macrumors 68020
Original poster
Oct 17, 2008
2,037
106
If there was something wrong with your logic board I'd be worried. As that was what I thought was wrong with my MP last night. A dead logic board is big buck$ to fix.

Maybe some of the slots on your risers are dodgy...
 

gpzjock

macrumors 6502a
May 4, 2009
798
33
The RAM modules work in matched pairs, if 1 dies its sibling can't function either. The DDR2 ECC RAM runs very hot and tends to fail over time anyway.
I have had 2 pairs of 2 GB modules fail in a 3,1 over 5 years. Memory America replaced the whole set each time under warranty.
If it keeps happening in the same slots replace the riser they are on.

http://manuals.info.apple.com/MANUALS/0/MA430/en_US/MacPro_Early2008_MemoryDIMM_DIY.pdf
 

sparkie7

macrumors 68020
Original poster
Oct 17, 2008
2,037
106
How hot does the RAM/riser area get? and what temo should it not go over? -- I have SMC fan installed - cool my machine that way...
 

gpzjock

macrumors 6502a
May 4, 2009
798
33
Peak temps under heavy load should not be above 85ºc for long periods. If you can keep them around 70ºc you should be fine for heat stress. Cleaning out the fans and enclosure internally can drop the temp 10º without fan adjustment. I do it annually.

Use the Hardware monitor to track ram temps.http://www.macupdate.com/app/mac/16609/hardware-monitor
 
Last edited:

AidenShaw

macrumors P6
Feb 8, 2003
18,625
4,627
The Peninsula
The RAM modules work in matched pairs, if 1 dies its sibling can't function either. The DDR2 ECC RAM runs very hot and tends to fail over time anyway.
I have had 2 pairs of 2 GB modules fail in a 3,1 over 5 years. Memory America replaced the whole set each time under warranty.
If it keeps happening in the same slots replace the riser they are on.

http://manuals.info.apple.com/MANUALS/0/MA430/en_US/MacPro_Early2008_MemoryDIMM_DIY.pdf
Perhaps in the Mac Pro - but I have 40 or so ProLiants from the same vintage with the same memory. I've had zero memory failures.

Perhaps the Mac Pro has inadequate cooling for the memory - in other words, the problem isn't the memory, it's the Mac Pro.
 

gpzjock

macrumors 6502a
May 4, 2009
798
33
Correct Aiden, the CPU coolers blows hot air straight onto the RAM risers. ECC RAM gets hot by itself, adding the CPU heat to it does not help.
 
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