Riazansary,  A couple things I see that would need to be clarified. In regards to processors, how many do you have installed? If you do indeed have 4 processors installed, then the minimum # of dimms that you can use is 16, as it is required to have 4 dimms per processor. If you are using 2 processors (1, 2) then the population would be A1-4 and B1-4. Table 3-2 on page 94 covers this, it  shows that the minimum number of dimms for 2 processors are 8, and 16 for 4 processors. - [URL]  Let me know what you see.
Hi everyone, I am running PowerEdge R815 with 128GB of memory (8Sticks of 16GB) I have tried every memory configuration i knew of and it still gives me 'memory configuration is not optimal, Press F1 to continue' upon reboot.  I tried  A1,B1 ---- A5,B5 C1,D1 ---- C5,D5 that should be the best according to the manual too but that even give the same issue. Can anyone plz tell me how to configure this to fix this issue? thanks,
PowerEdge R815 Optimal Memory Configuration