MacPro3,1 DIMM riser B not working

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Level 1

24 points

MacPro3,1 DIMM riser B not working

I just bought 4x2GB RAM sticks (8GB total) for my Mac Pro to add to my existing 2x1GB and 2x2GB setup for a total of 14GB. All the old RAM was in riser A (2 2 1 1), so I put the new RAM in riser B. I have the same problem outlined in this archived post: Mac Pro not recognising 2nd DIMM Riser

As the other poster said, my Mac is not seeing the new RAM, and System Profiler shows a failed power on self-test for reason "memory". My Mac only sees the original 6GB.

Here's the error message in System Profiler:

Last Run:	9/17/15, 6:47 PM
Result:	Failed
Failure Type:	Memory

Las

Memory Slots:

DIMM 1/DIMM Riser B, DIMM 2/DIMM Riser B, DIMM 3/DIMM Riser B, DIMM 4/DIMM Riser B

Running OS X 10.10.4. MacPro3,1 (8-core 2008 model).

I tried swapping the riser boards, putting the riser with the new 8GB in slot A and putting the riser with the old RAM in slot B. My Mac sees the 8GB but not the original 6GB. So the riser board itself can't be the problem. There's something going on with the slot. Already tried a PRAM reset. Any other fixes I can try? I can't readily run AHT, but no matter what result I get from it, it wouldn't fix the problem anyway. I'm assuming it'll just say "failed" or something.

Thanks in advance.

- Alec

Posted on Sep 17, 2015 9:09 PM

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Answer 1

lllaass

Level 10

210,513 points

Sep 18, 2015 6:14 AM in response to AlecZ64

What are the detailed specs for all the memory?

Seems lie they are different and when installed together they do not work. Couolbe due to different speeds of the memory or other differences.

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Answer 2

The hatter

Level 9

61,031 points

Sep 18, 2015 10:19 AM in response to AlecZ64

you did not try with just new FBDIMMs.

Also a link of source RAM.

6667's work, run colder, are cheap and abundant on ebay now, mostly server pulls.

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Answer 3

AlecZ64 Author

Level 1

24 points

Sep 18, 2015 7:17 PM in response to The hatter

Here's the RAM I bought: http://www.ebay.com/itm/350618750043?_trksid=p2057872.m2749.l2649&ssPageName=STR K%3AMEBIDX%3AIT

800MHz; my old RAM is also 800MHz. I doubt it has to do with the new RAM because I experienced this problem with my old RAM too. I was trying to split it across both risers (2 2 x x | 1 1 x x) since the manual actually says to do that, and only riser A was working.

I am currently running with the new 8GB in riser A and the old 6GB in riser B, inactive. (2 2 2 2 | 2 2 1 1).

(2 2 1 1 | 2 2 2 2) also works, leaving the new 8GB inactive in riser B.

So yeah, from my tests, it seems that whatever is in riser slot B just won't work, regardless of which RAM or riser board I use. I don't quite follow what you're suggesting I should try. You mean try only the new RAM in riser B and leave riser A empty?

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