I have a mid-2008 MacPro with 20GB RAM (8 slots with 4-1 GB DIMMs and 4-4GB DIMMs). I recently was given 2 more 4GB DIMMs. However if I remove 2-1GB DIMMs and replace with the new ones, the computer only recognizes the previous 4-4GB DIMMs and my RAM drops to 16GB. Any solution? I know all the DIMMs work and I arranged the DIMMs symmetrically as recommended.
macbook pro, Mac OS X (10.5.5)
What are the details of the new RAM and the old RAM? Sounds like they are different besides capacity
If you remove all RAM and only install the two new ones does it work OK (it will be slow with only 4 GB).
How do you know the two new ones work>
The old RAM (4GB) came with the computer. The 4GB DIMMs are komputer bay 4GB PC2-6400F 240 pin CL5 800MHz ECC fully buffered 2Rx4. All the 4GB DIMMs are Komputer Bay. I put 4 DIMMs in 6 months ago to raise my RAM to 20 GB.
I also bought 8GB (2X 4GBfor a pre 2008 MacPro at work). The work machine is being replaced so I removed the RAM and brought them home. They worked fine at work. I haven't put the new only RAM in at home. I just know they worked fine at work. The strange thing is the 2-1GB DIMMs aren't recognized either when I put in the new DIMMs.
What if in the one riser you remove the 1GB sticks and only use the two new 4 GB sticks?
It worked! I now have 26GB RAM.
Thank you very much for your help.
mid-2008 MacPro with 20GB RAM
