I own an optiplex 380 which currently has 2x2GB DDR3 RAM, now I am willing to upgrade to 8GB and I tested a Kingston ValueRam of 4GB @ 1333Mhz and my system beeped with 1 and 3 LED lights lit. So does it means 1333mhz is too high? Should I try to find a 1067mhz one?
late answer however would help next users. Maximum ram is 8GB. Any frequency would be supported but RAM will run at the chipset's speed that is to say 1067Mhz, no more. Problem with your ram comes with the modules density. Funny that people assert that 4gb is the max. I have here on my left knee an optiplex 380 running with 2x4gb of 1600mhz crucial ballistix sports, running at 1067mhz.
Judging by the Manual I would say that your RAM is not compatible.
Maximum memory: 4GB @ 1067 MHz. That means that each RAM module bank can support a maximum of 2GB. So 2x2GB @ 1067 MHz is the best you can get with this board. If you look at page 12/13 you can see the explanation of the error code
Their seems to be some conflicting information with the dell manuals: check out the max memory from the dell optiples 380 setup and Features Information pdf - http://downloads.dell.com/manuals/all-products/esuprt_desktop/esuprt_optiplex_desktop/optiplex-380_setup%20guide_en-us.pdf
Memory module connector 2 DIMM slots Memory module capacity 1 GB, 2 GB, or 4 GB Memory type 1067 MHz DDR3 Minimum memory 1 GB Maximum memory 8 GB
and from Dell™ OptiPlex™ 380 Service Manual—Mini-Tower
Memory Connectors two Capacity 1 GB or 2 GB Type DDR3 SDRAM (non-ECC memory only) 1067 MHz Minimum memory 1 GB Maximum memory 4 GB
bottom line is that the memory must low density (chips on both sides of the dimm), non-ecc, 1067 mhz (pc3-8500). Where these manuals differ is that one list max memory as 8gb and the other 4gb.