Mac Pro does not recognize Ram on DIMM Riser B card

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Mac Pro does not recognize Ram on DIMM Riser B card

I just recently purchased 2 x 2 gb ram to add to the existing ram ( 4 x 512mb on riser card A). I installed the new ram in slots 1 & 2 on riser card B. Started the computer. Checked the System Profiler and it showed all DIMM Riser A/DIMM 1,2,3 & 4 each with a 512mb DIMM, DIMM Riser B, DIMM 1,2,3,& 4 empty. I swapped DIMMs from A to B Risers, and only DIMMS on Riser A appear, DIMMB Riser B shows all empty. I swapped the cards around and again only DIMM Riser A shows Ram to be installed and tried different combination of the pairs of cards. Everything worked in Riser A and Riser B as all empty.

Any one have any ideas on what is wrong?

Mac PRO, Mac OS X (10.5.1), Mac Pro 2.66

Posted on Dec 8, 2007 12:21 PM

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Answer 1

Dec 8, 2007 1:38 PM in response to marvin_z

Bad news is, if you swapped riser cards and it was still a riser B problem then you most likely have a bad riser slot on the MLB ( $$$ )

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Answer 2

Dec 9, 2007 7:49 AM in response to marvin_z

System Profiler doesn't react to the changes.
But what does 'about this mac' show?

i ask because, i just added RAM and it works fine. The 'about this mac' indicates 8gb, but the like you, the system profiler shows the original 2x512 configuration.

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Answer 3

marvin_z Author

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Dec 9, 2007 1:18 PM in response to marvin_z

The "About this Mac" only shows only the amount in the upper Riser A card and not what is Riser B card. I have a total of 5gb in A card and 1gb in B card, "about this Mac" only shows what is in A card, and will only show what is in A card when I changed the configuration around.

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Answer 4

The hatter

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Dec 9, 2007 1:52 PM in response to l_elephant

Press the SMC Reset button.

System Profile reports the "device tree" stored in NVRAM.

Look under Memory setting. Any errors there?

Type this in Terminal:

system_profiler

That will give full list.

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Answer 5

marvin_z Author

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Dec 9, 2007 2:17 PM in response to The hatter

I already pressed the SMC, and did not change anything. I typed in system_profiler in Terminal and it showed no errors, and shows Card A to have the ram that is installed but Card B shows all slots as empty when slots 1 & 2 each have a 512mb Dimm installed in the slots. If I swap the Riser Cards around it shows just what is on the A Riser.

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Answer 6

Dec 9, 2007 6:54 PM in response to marvin_z

Assuming you mean that it "shows what is on the A riser" as what is on the original A riser in the lower slot it sounds like a bad riser card. You need to contact Apple to get a replacement.

If you mean it shows what is on the riser in the upper slot it is a bad mother board and you'll need to contact Apple to have the motherboard replaced.

Message was edited by: Martin Pace

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Answer 7

marvin_z Author

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Dec 9, 2007 7:04 PM in response to Martin Pace

maybe i was not clear enough in my last post. When I referred to the A & B cards I meant A as the upper slot and B as the upper slot. I can change the cards from upper and lower slots and change the the order and amount of ram on the cards but it only reads what is in the upper Slot (A). It always shows that the lower card (B) has all the slots on it as empty, no errors shown in the terminal/

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Answer 8

Dec 9, 2007 7:11 PM in response to marvin_z

That means that it is a motherboard problem and you'll have to send it in to Apple or an Apple authorized service center for repairs.

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