Strange RAM error during MacPro Diagnostic initialisation

Question

Hi there,
we've just received our brand new Mac Pro Server (2010) 2,4GHz Intel 8-Core Xeon (two Quad-Core Xeon E5620 "Westmere") and (8x4GB) DDR3-1066/1333R ECC Original Samsung Memory from an authorized Mac Reseller.

Once the MacPro Hardware Diagnostic Selfcheck has been initialized, we do get a memory error message for all memory modules: Memory - DIMM 1 (test 50) - Memory - DIMM 1 Check SMBIOS for devices that are flagged as having an error. (see above). Running the full Hardware Diagnostic check works seamless and the test quits without any error.
Although we've successfully installed all memory modules (8x4GB), the Apple System Profiler recognized 28 GB RAM at first. Resetting P-RAM and SMC solved the problem. 32GB RAM show up.
We are really concerned about the memory error message. What does it mean?
The memory modules has been tested by our reseller and are officially supported. When I startup the MacPro Hardware Diagnostic Selfcheck with the default Apple memory (2GB), no error shows up.
I really appreciate any comments on this.



Memory - DIMM 1 (test 50) - Memory - DIMM 1

Check SMBIOS for devices that are flagged as having an error.


Error - DIMM size miscompare.

T E S T F A I L E D -
Memory - DIMM 2 (test 50) - Memory - DIMM 2
Check SMBIOS for devices that are flagged as having an error.


Error - DIMM size miscompare.

T E S T F A I L E D -
Memory - DIMM 3 (test 50) - Memory - DIMM 3

Check SMBIOS for devices that are flagged as having an error.


Error - DIMM size miscompare.

T E S T F A I L E D -
Memory - DIMM 4 (test 50) - Memory - DIMM 4

Check SMBIOS for devices that are flagged as having an error.


Error - DIMM size miscompare.

T E S T F A I L E D -
Memory - DIMM 5 (test 50) - Memory - DIMM 5

Check SMBIOS for devices that are flagged as having an error.


Error - DIMM size miscompare.

T E S T F A I L E D -
Memory - DIMM 6 (test 50) - Memory - DIMM 6

Check SMBIOS for devices that are flagged as having an error.


Error - DIMM size miscompare.

T E S T F A I L E D -
Memory - DIMM 7 (test 50) - Memory - DIMM 7

Check SMBIOS for devices that are flagged as having an error.


Error - DIMM size miscompare.

T E S T F A I L E D -
Memory - DIMM 8 (test 50) - Memory - DIMM 8

Check SMBIOS for devices that are flagged as having an error.


Error - DIMM size miscompare.

T E S T F A I L E D -

Answer 1

Deal with the seller. They sold a set, OWC and others like Crucial would want to inspect the full set.
If you want to play games, go ahead; try one pair at a time and play DIMM slot shuffle and see if the symptoms change, and consider anything you do to be corrupt in the meantime.
AHT is good at spotting physical/mechanical defects iwth the processor daughter card that houses the cpu and RAM.
Nehalem/Westmere memory controller is now part of the processor and is why you (Apple, or if someone reseats cpu) has to be careful of those very tiny pins some of which handle RAM.
Personally, 2.4GHz is not what I would have gone after. MHz still matters and a 6-core 3.33 is a nice fast system and can still accept 32GB (but that is all).
The best guide to Mac Pro, by topic, review & articles, & date:
http://macperformanceguide.com/