I recently decided to buy an extra 8GB of DDR3 1333 memory (2x 4GB) to make it a total of 16GB. I inserted the new memory so all of the A slots are filled and 1 of the B slots are filled. It does work but it will not run at 1333MHz but 800MHz. There are no options in the bios to change this so can someone help me?
Memory population rules on this board is kind of complex. Memory working frequency is defined by following factors:
1. Number of DIMMs on a channel. Only one DPC (DIMM Per Channel) may work at 1333MHz.
2. Organization of the DIMM. A single Quad-Rank DIMM on a channel is limited to 1066MHz.
The rules above (and more) are documented in http://www.intel.com/support/motherboards/server/s3420gp/sb/CS-030742.htm S3420GP TPS, section 3.2.4. An easier way is to download and run the http://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=17625&keyword=%22memory+configuration... Intel Memory Configuration Tool, and see what kind of memory configuration meets your requirements.