Mac Pro not seeing all the ram

[uMac]

Basically is this a Mac Pro issue or Ram Issue.

I recently got 8GB of ram (4x4GB) and Put them in the risers as so. But my computer will not seem to acknowledge 2 of the sticks as 2GB, but rather one...

Now I played a bit of musical ram but the computer will only see 7GB out of the 9 (so a set of 2GB shows up as 1GB). I think 1 stick may be only 1GB or is this a computer issue? I would like to know as I will send the two chips back I think are the cause of this if its Ram and not some 'Mac Pro' thing.

Is there a way to test the ram?

Thanks so much for any help you can give.

Riser A

2GB - New (Currently Mac thinks it 1GB)
2GB - New (Currently Mac thinks it 1GB)
512GB - Original
512GB - Original


Riser B
2GB - New
2GB - New
Empty
Empty

 

[TEG]

The Risers need to be equal.

Riser A
2GB
2GB
512MB
-----

Riser B
2GB
2GB
512MB
----

TEG

 

[uMac]

TEG you may be right on the risers need to be equal, but the ram needs to be in matched pairs.

 

[pastrychef]

The Risers need to be equal.

Riser A
2GB
2GB
512MB
-----

Riser B
2GB
2GB
512MB
----

TEG

This is incorrect. The way that uMac had it plugged in is the proper way.

 

[TEG]

TEG you may be right on the risers need to be equal, but the ram needs to be in matched pairs.

But in matched pairs across the risers. The computer basically sees the risers as the only two memory busses, they must be equal and the matched pairs are between slots. So Slot 1A and 1B must match, 2A and 2B must match, etc.

TEG

 

[uMac]

After another round of Moving chips I have concluded that its 1 pair is only reading 1GB per chip (A lose of 2GB).

So I'm going to contact the seller and ask for a refund/replacement.