Mac Pro (early 2008) RAM Problem

[wellenreiter]

Hey everyone,
i got a problem with my Mac Pro.

I installed 8x1GB RAM on it but i can only see 6GB at the System Profiler.
The two hidden RAM-modules are perfectly working if i plug them on Riser 1 and 2 in Dual-Mode (Riser A - DIMM 1 // Riser B - DIMM 1).

The Modules are all grouped in pairs.
If i change the position of the not working RAM-Modules, they arn't working at the new place.

What can i do, to fix this problem ??

I have checked all RAM-Modules in the 2GB Mode (see Screenshot 02).

Here is my Sytem Configuration:

Mac OS X 10.6.8
2,8GHz Quad-Core Intel Xeon


The new RAM-Modules were bought special for Mac Pro (early 2008) and are FB-DIMMs with ECC.

Sorry for my bad englisch, i'm german

Thanks for your replys,
cheers

 

[wafl iron]

does the same behavior happen with any other pair when you do the same experiment using the same slots?

If not, then i would see if your ram seller has a replacement policy.

 

[wellenreiter]

First, Thanks for the fast answer ;-)

I forgot to say that i already resent the (in my opinion)damaged RAM-modules back to the Reseller. He gave me new one but they didn't work too.

All the other Modules are working perfectly in every slot on every riser.

 

[Neodym]

Sounds like your memory daughterboard could be damaged. You could try to have it repaired or to get bigger modules and have only 4 slots populated. The latter would also improve Ram access due to lower latency (inherent in FB-DIMM's).

(German translation: Möglicherweise ist die Platine defekt, auf der die Module nicht funktionieren. Kannst versuchen, das reparieren zu lassen oder größere Module kaufen und nur 4 Slots bestücken. Letzteres würde auch den Ramzugriff verbessern, da die bei FB-DIMMs systembedingte Zugriffslatenz verringert würde).

 

[wellenreiter]

hmmm ... i thought the daughterboard could be damaged ... but when i change the position of the damaged RAM, they cant be seen at the new position (in Profiler). For example:

This is my status:
Riser A - DIMM 1 - OK
Riser A - DIMM 2 - OK
Riser A - DIMM 3 - OK
Riser A - DIMM 4 - OK

Riser B - DIMM 1 - empty
Riser B - DIMM 2 - empty
Riser B - DIMM 3 - OK
Riser B - DIMM 4 - OK

If i change Riser B - DIMM 1 and Riser B - DIMM 2 to any other position it looks like this:

Riser A - DIMM 1 - OK
Riser A - DIMM 2 - OK
Riser A - DIMM 3 - empty
Riser A - DIMM 4 - empty

Riser B - DIMM 1 - OK
Riser B - DIMM 2 - OK
Riser B - DIMM 3 - OK
Riser B - DIMM 4 - OK

(only for example!!! I could try every position)

Maybe your' right to buy new RAM-Modules with 4x 2GB ... ;-)

but thanks for your answer

 

[ianthor7]

I'm having the same issue

I have the same computer and I'm trying to max out the RAM. Were you able to discover a solution to this issue?