Restored Dell Optiplex 990-D WA1-0376 Desktop PC with Intel Core i7-2600 Processor, 8GB Memory, 2TB Hard Drive and Windows 10 Pro (Monitor Not Included) (Refurbished) - Walmart.com
Problems adding RAM to Optiplex 990 Bios Revision A23 - Dell Community
CMS 8GB (2X4GB) DDR3 10600 1333MHZ Non ECC DIMM Memory Ram Upgrade Compatible with Dell® Optiplex 990 Dt/Mt/Sff, Ultra - A69 at Amazon.com