Solved: Optiplex 7020 MT, CPU upgrade? - Dell Community
Dell OptiPlex - Wikipedia
Optiplex 3020 graphics card upgrade - Dell Community
Dell Optiplex 3020 SFF Computer PC, Intel Core i3-4130 3.4Ghz, 8GB RAM, 500GB SATA HDD, DVD Windows 10, includes 19" LCD, keyboard, and mouse, 1 year warranty - Walmart.com