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Bad RAM or Bad Risers?

My Early 2008 Mac Pro works fine, then suffers a series of crashes. I then pop out the risers and shuffle the RAM (move them to a different rider and in a different position), and then my Mac Pro works fine for a few months. Then it happens all over again. I'd like to solve this problem once and for all. I've read different threads on there and can't quite figure out if it is the RAM or the Risers. Any insights? Any tests I can do to determine the problem?

Posted on Mar 19, 2015 9:54 AM

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Posted on Mar 19, 2015 5:18 PM

The RAM DIMMs are millions of times more likely to be the cause of the problem compared to the riser-cards.

Any tests I can do to determine the problem?

Yes, your Mac checks each and every Read from RAM Memory with a Hardware assist built into the Xeon Processor, corrects single-bit errors in Hardware on the fly, and tabulates that information in the background for you. All you need to do is your normal work, and from Time-to-Time invoke or refresh that STATIC display.


 menu > About This Mac > ( More Info ) > ( Report ) > Memory

User uploaded file


graphic from anandtech.com


And now, the leap of faith:

• modules showing Errors are BAD, and should be replaced.

• modules whose slots show as Empty, were so BAD, they threw an error (possibly a correctable error) during the first few seconds of the Power-on Self Test, and will therefore not be used by the System.


If an uncorrectable error occurs, your Mac is designed to kernel panic with a machine check, typically detected by multiple processors. Occasionally (but not often) the exact module is called out. This keeps a memory error from poisoning your data.

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Question marked as Best reply

Mar 19, 2015 5:18 PM in response to Mike Paunovich

The RAM DIMMs are millions of times more likely to be the cause of the problem compared to the riser-cards.

Any tests I can do to determine the problem?

Yes, your Mac checks each and every Read from RAM Memory with a Hardware assist built into the Xeon Processor, corrects single-bit errors in Hardware on the fly, and tabulates that information in the background for you. All you need to do is your normal work, and from Time-to-Time invoke or refresh that STATIC display.


 menu > About This Mac > ( More Info ) > ( Report ) > Memory

User uploaded file


graphic from anandtech.com


And now, the leap of faith:

• modules showing Errors are BAD, and should be replaced.

• modules whose slots show as Empty, were so BAD, they threw an error (possibly a correctable error) during the first few seconds of the Power-on Self Test, and will therefore not be used by the System.


If an uncorrectable error occurs, your Mac is designed to kernel panic with a machine check, typically detected by multiple processors. Occasionally (but not often) the exact module is called out. This keeps a memory error from poisoning your data.

Bad RAM or Bad Risers?

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