I'm having trouble with my RAM upgrade. I just bought a new 2.8 dual quad core MacPro with 2GB of RAM (2x1GB). I bought an additional 4GB RAM (2x2GB) from TransIntl. However, the most my Mac will see is 4GB, no matter how I configure the RAM. This is what I've tried: Original Configuration: Riser A1: Apple 1GB Riser A2: Riser B1: Apple 1GB Riser B2: Total memory visible by System Profiler: 2GB (1 in Riser A, 1 in Riser B) =========== Apple Suggested Configuration: Riser A1: Apple 1GB Riser A2: Apple 1GB Riser B1: TransIntl 2GB Riser B2: TransIntl 2GB Total memory visible by System Profiler: 2GB in Riser A, none in Riser B =========== Alternate Test: Riser A1: TransIntl 2GB Riser A2: TransIntl 2GB Riser B1: Apple 1GB Riser B2: Apple 1GB Total memory visible by System Profiler: 4GB in Riser A, none in Riser B =========== I've reseated both risers and all the RAM but to no avail. After I tried Apple's suggested configuration, I ran the Hardware Test disk. It saw all the RAM, however it would only identify the Apple RAM with part numbers. Plus, it only calculated a total of 2GB. When I restarted, only the Apple RAM was visible in the System Profiler, all the other slots reported as "empty." I've returned the system to the original configuration (1 in Riser A, 1 in Riser B) and it correctly reports 2 GB total. I thought at first the TransIntl RAM was faulty, but it does show up correctly in the Alternate test. Is it possible to load all the RAM on one Riser for testing purposes? Or maybe place them in different slots on Riser B?