Dell OptiPlex 7040M vs. Dell Vostro 3900g
Comparison and Differences
Differences between Dell OptiPlex 7040M and Dell Vostro 3900g
If you are looking for a more modern desktop, then you should go with the Dell OptiPlex 7040M which was released in 2015. The Dell Vostro 3900g is older and entered production in 2014.
If you are looking for the smaller form factor the Dell OptiPlex 7040M is the right one for you. It is smaller than the Dell Vostro 3900g and will fit more easily under your desk.
Processor
Usually the newer the generation of the CPU, the better the performance and efficiency is. If your budget allows it, you should go with the Dell OptiPlex 7040M as it is running a newer generation CPU. This is not to say that Dell Vostro 3900g is bad - it can still run some powerful CPUs, albeit being an older generation.
Memory
Both models have have equal amount of ram slots (2 RAM). Usually two RAM slots are more than enough for most cases. However, the count should be taken into account when planning how much and what combination of RAM you are going to need for your system.
The Dell OptiPlex 7040M is using the faster 2133 MT/s RAM. The Dell Vostro 3900g is slower by supporting RAM speeds of up to 1600 MT/s. Additionally, if you will be needing a lot of RAM, better go for the Dell OptiPlex 7040M as it has the ability to run 32 GB of RAM. The Dell Vostro 3900g can do a bit less at max 16 GB. Most of the times, this should be sufficient for the majority of users.
Ports
In total the Dell Vostro 3900g has 8 USB ports. The Dell OptiPlex 7040M is inferior in this regard and packs 6 USB ports. In any case, if you miss USB ports, you can always purchase a USB hub. 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 7040M has a DisplayPort. The Dell Vostro 3900g does not have one? Don't worry though, nowadays video adapters are cheap and you can get almost any combination of conversion types.
In case your monitor supports HDMI only, you will be happy to hear that both models come with an HDMI port.
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 Vostro 3900g is better equipped as it comes with 4 SATA slot(s), while the Dell OptiPlex 7040M has 1 slot(s).
If you want the fastest transfer speeds for your SSD, an M.2 interface is crucial. Thus, if the M.2 SSD slot is a mandatory requirement for you, go with the Dell OptiPlex 7040M. Sadly, the Dell Vostro 3900g has no such slot, and you will be forced to use the SATA interface instead.
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
Having a Power Supply Unit with high power rating is important, if you are going to use components which require extra power. The Dell OptiPlex 7040M comes with a decent 65 Watt PSU, but the Dell Vostro 3900g has a more powerful one rated at 300 Watts. Choosing either one depends on your specific requirements and use case. Also don't forget that some models might have more than one PSU option - try to always get the most powerful one, especially if you plan to upgrade to a powerful GPU.
Motherboard
