Don't mix desktop RAM into a server.

No. Non-ECC desktop DDR3 won’t work in a PowerEdge T320, and forcing it can cause boot failures or damage.

The T320 needs registered ECC (RDIMM) memory. Desktop RAM is unbuffered (UDIMM) and usually non-ECC. The memory controller expects the extra chip for error correction and the registration buffer. Plugging in a stick of plain desktop DDR3 is like putting gasoline in a diesel engine — physically fits, electrically wrong. The system will either refuse to boot or hang at POST.

You can mix different capacities and speeds of RDIMMs, as long as they’re all ECC registered. But don’t cheap out on server RAM. Buy used 8GB or 16GB RDIMMs on eBay for pennies. They’ll drop right in and work.

The T320 isn’t a desktop PC. Treat it like a server, even if you got it cheap.