A semi or fully modular power supply is a power supply that allows for better cable management inside the case, as it allows only the cables that we will use in Cable Management to be connected to the power supply. The difference between semimodular and fully modular is in the possibility of decoupling or not decoupling all cables from the power supply.
Semi-modular power supply
Semi-modular power supplies are those where some cables are connected to the internal circuit of the power supply without the possibility of being removed, such as the main 24-pin cable, the PCI and the 8-pin cable that powers the processor. However, the remaining cables can be removed and replaced as needed.
Fully modular power supply
Full-Modular power supplies are power supplies where you can remove all cables, without exception. Making handling and installation more convenient when managing cables.
The advantages of modular power supplies
The modular power supplies, in addition to ensuring good aesthetics to the computer and good cable management, also allow for better air circulation inside the case, which in turn improves hardware cooling somewhat, and a well cooled one increases the life of some components.
Another advantage of this type of power supply is that it allows quick and easy access to internal peripherals, because due to the possibility of better cable management, it is easier to remove or install new peripherals.