PowerEdge R220 Installing Slots with Different Memory Capacities

Yes, you can use that configuration. The larger 8 GB DIMMs need to be in the white slots. 

Here is a link the manual and an excerpt of the memory info below:

ftp://ftp.dell.com/Manuals/all-products/esuprt_ser_stor_net/esuprt_poweredge/poweredge-r220_Owner's%20Manual_en-us.pdf

This system supports Flexible Memory Configuration, enabling the system to be configured and run in any valid chipset architectural configuration. The following are the recommended guidelines for best performance:

•x4 and x8 DRAM based DIMMs can be mixed.

•Populate all sockets with white release tabs first, and then black.

•Populate the sockets by highest rank count in the following order – first in sockets with white release levers, and then black. For example, if you want to mix quad-rank and dual-rank DIMMs, populate quad-rank DIMMs in the sockets with white release tabs and dual-rank DIMMs in the sockets with black release tabs.

•Memory modules of different sizes can be mixed provided that other memory population rules are followed (for example, 4 GB and 8 GB memory modules can be mixed).

•If memory modules with different speeds are installed, they will operate at the speed of the slowest installed memory module(s) or slower depending on system DIMM configuration.

 

Please let us know if you need further info that we can help with.