Dell OptiPlex 390 DT vs. Dell OptiPlex 990 DT
Comparison and Differences
Differences between Dell OptiPlex 390 DT and Dell OptiPlex 990 DT
Both computers, the Dell OptiPlex 390 DT and the Dell OptiPlex 990 DT, were released during the same year - 2011.
Both models have the same form factor, meaning reoughtly they have the same phiysical size and form.
Processor
The two models have the same generation of Intel processors. We think that the 2 generation of Intel Processors have enough power to execute all of the home and office tasks that most people will care to do.
Memory
The Dell OptiPlex 990 DT has 4 RAM slots while the Dell OptiPlex 390 DT has only 2 slot(s). This is not something to worry about. Just make sure you take it into consideration when planning how much RAM you are going to use.
None of the desktops has an advantage when it comes to the speed of the RAM being used. Both models support RAM speeds of up to 1333. Additionally, if you will be needing a lot of RAM, better go for the Dell OptiPlex 990 DT as it has the ability to run 16 GB of RAM. The Dell OptiPlex 390 DT can do a bit less at max 8 GB. Most of the times, this should be sufficient for the majority of users.
Ports
Both models have the same amount of USB ports for total count of 8. If this is not enough, using a USB hub is always a viable option. None of the desktop models has a USB 3.1 port (10Gb/s), so if you need a fast connection to your peripherals, like external Solid State Drive, you will need to look elsewhere.
Unfortunately, only the Dell OptiPlex 990 DT has a DisplayPort. The Dell OptiPlex 390 DT does not have one? Don't worry though, nowadays video adapters are cheap and you can get almost any combination of conversion types.
The Dell OptiPlex 390 DT comes with an HDMI port, while the Dell OptiPlex 990 DT does not support the interface. Of course missing HDMI port is something that can be easily fixed with a good adapter (e.g. DisplayPort to HDMI).
SATA ports are placed on the system board and it is where you connect your HDD, SSD and Optical Disk Drives. More SATA slots will allow you to have more drives running at the same time. In this regard the Dell OptiPlex 390 DT is better equipped as it comes with 4 SATA slot(s), while the Dell OptiPlex 990 DT has 3 slot(s).
M.2 SSD interface allows you to transfer data with higher speeds compared to the old SATA interface. Unfortunately, neither the Dell OptiPlex 390 DT, nor the Dell OptiPlex 990 DT has one. However, you can still use a SATA SSD drive which should give you satisfactory performance.
Make sure that the available M.2 slot supports the PCIe (also called NVMe) interface. This is important as there are M.2 slots which support only the inferior SATA III interface. For comparison, the SATA III interface has max speeds of 6Gb/s, while the PCIe 3.0 x4 will support speeds up to 32Gb/s!
Power Supply
Looking at the Power Supply Unit (PSU) of the two models we don't see any differences. For either of them you get a maximum power of 250 Watts. However be careful, many models have more than one power supply option. When buying your computer, it is a good idea to get a version with the most powerful PSU. This will potentially allow you to upgrade to a more powerful GPU for example.
Motherboard
