A weird issue with my RAM?

[ZigZagLens]

Hey folks...

I have a new Mac Pro. Purchased it last week with 1GB RAM (Apple 512x2) and bought 4GB from OWC. All was working fine over the weekend.

The 4GB arrived today (4x1GB).

Here's the oddity...

When I install it like this:

Riser A, Slots 1 & 2: 1GB OWC DIMMs
Riser A, Slots 3 & 4: 1GB OWC DIMMs

Riser B, Slots 1 & 2: 512 Apple DIMMs
Riser B, Slots 3 & 4: Empty

then OS/X sees all 5GB and things seem to operate normally.

However, per this graphic I found in my searches here, I noted that the RAM is ideally installed the other way, below.

BUT, when I install as such:

Riser A, Slots 1 & 2: 1GB OWC DIMMs
Riser A, Slots 3 & 4: 512 Apple DIMMs

Riser B, Slots 1 & 2: 1GB OWC DIMMs
Riser B, Slots 3 & 4: Empty

The machine does not see / recognize the RAM on Riser B. In this configuration, it reports that Riser B has all four slots empty (so it reports 3GB RAM installed.)

I have repeatedly checked that everything is seated properly.

Any clues what is up?

Thanks all.

 

[iSavant]

should be working as you think it should... my two week old 2.66 came witth 1 GB and I added 4x1 GB OWC like so:

a1 1 gb
a2 1 gb
a3 512 mb orig
a4 512 mb orig
b1 1 gb
b2 1 gb

recognizes as 5 gb as expected.

Just one thought on this... I do not know if there is any difference in circuitry between the a riser and the b riser,,, is it possible your a and b risers have been switched and would it make a difference anyway?

Hope you get this figured out soon, good luck!

 

[ZigZagLens]

should be working as you think it should... my two week old 2.66 came witth 1 GB and I added 4x1 GB OWC like so:

a1 1 gb
a2 1 gb
a3 512 mb orig
a4 512 mb orig
b1 1 gb
b2 1 gb

recognizes as 5 gb as expected.

Just one thought on this... I do not know if there is any difference in circuitry between the a riser and the b riser,,, is it possible your a and b risers have been switched and would it make a difference anyway?

Hope you get this figured out soon, good luck!

Thanks for the prompt reply. I'm tempted to just switch it back to the "wrong" way to get my 5gb!

But yep, that's how mine is at the moment (like yours) and she thinks she has 3gb. I wonder if the risers were switched. Should it matter? Hmm again...

 

[ZigZagLens]

It's looking like a bad stick. I rearranged things several times, mixed up the pairs, moved them all around - and it seems that wherever I put a certain stick, the pair registers as empty. Must have been a fluke that it worked fine initially, until I rearranged them that first time. I'm also learning about the little red lights .. and they are following the bad stick..

So, I'll be exploring the OWC exchange policy tomorrow ... *sigh*