Memory modules not getting detected in Mac pro

[Agriya]

Hello, I have a Mac Pro which is powered by Intel Quad core with 8GB RAM in 4 x 2GB DIMM slots. The operating system on the Mac Pro was Mac OS X 10.5 which I recently upgraded to Mac OS X 10.6 but after upgrading the operating system on the computer I am getting a very unusual error. After upgradation I am getting a memory configuration error message. The system prompts that the it is loading a sub optimal configuration in which only 2gb ram is detected. The other Ram chips are not detected by the system. I cant figure out if the problem is due to the operating system upgrade or firmware update because I performed both the updates on same day. Therefore if any one is facing problem like Memory modules not getting detected in Mac pro then please share some information. Any help is appreciated.

[Fabian]

It is possible that the other system RAM chips of your system have gone bad and hence the system is not detecting them. RAM is the most volatile memory in the computers which can get corrupt or can develop fault if there is power fluctuation. I would suggest that you get the RAM chips which are not getting detected as they may be faulty. Open the Mac pro and check the RAM chips one by one and check if the system boots or not. If the system does not boot for a particular chip then chip is faulty and needs to be discarded.

[RoninBlade]

Operating system upgrade can be the reason that the system is not able to detect the RAM. If all the files which are required for the operating system to work properly are not copied on the hard drive then the operating system will give errors like the one which you are facing. If you have the install disk of the operating system which you are using then insert it in the drive and boot the system from the it. Install the operating system again using Install/Archive mode which will enable you to use the installed applications on the new operating system. After reinstalling the operating system check if the system is able to detect the RAM or not.

[deoWo]

Many of the problems of the Mac systems are solved by doing a PRAM reset. If the system is not able to access the system RAM properly it can be because of the invalid entries get stored in the RAM. If the RAM gets flooded with the invalid entries then you will have to clear the RAM manually. To clear the invalid entries you will have to perform PRAM reset. To perform PRAM reset, follow the steps below :-
1. Locate and find the following keys (Apple, Option, R and P)
2. Press and hold the following keys while pressing the power button.
3. Keep the keys pressed till 3 startup chimes are heard.
4. Release the keys when the 3rd startup chime is heard and then let the system boot normally, check if all the RAM is detected by the system or not.

[T.J.]

I think the problem which you are facing is due to faulty logic board. All the operations that are performed by the computer are controlled by the logic board. If the logic board itself is faulty then the user will face errors like the one which you are facing. There is a possibility that the DIMM slots which are used to connect the RAM are faulty and hence the system is not able to detect the exact capacity of the RAM. Take the computer to the Authorized Apple service center and get the computer checked. If the logic board is faulty then you will have to replace it.