Installed 8gb but it's only showing 6gb

Hello all, I'm pretty new here to macforums. I searched for this answer but didn't find it so I hope I'm not repeating a question.

I have a Mac Pro (early 2008) it had the original 2gb (2x1gb) of RAM. I bought 8gb (4x2gb) from 8GB FULLY BUFFERED PC2-6400 DDR2 ECC (FB-DIMM) 800MHz SPECIAL APPLE KIT (Four modules 2GB) MB194G/A I spoke to customer support and they assured me that it was the right kind that I needed. I separated them evenly so on each card I now have 2-2gb & the original 1-1gb.

However it's showing in "About this Mac" tab that I only have 6gb of RAM when I should have 10. What am I doing wrong?

When you install the RAM, there are specific slots/order which you need to populate. Also, you may have a bad stick, this does happen from time to time.

Review the MacPro user manual for your model (I have the same one) about installing memory. If you have the correct configuration, run the Hardware test provided with your OSX install disks and it will tell you if a stick is bad.

Welcome to the forums!