We are all used to ATX format power supplies, not because they are the standard itself but because they are the most widely used standard. However, there are also power supplies in SFX format, based on the mini ITX standard and with other characteristics that we will explain to you below, as well as we will tell you in which cases you will need one of these sources and not a standard ATX .
As you know, in the hardware world there are different formats and standards, all of them with certain characteristics and peculiarities. Best SFX Power Supply is a format of power supplies that refers to their size, and that are based on the mini ITX standard instead of the ATX but that, electrically, are practically identical.
SFX is a Small Form Factor (SFF, or Small Form Factor) power supply enclosure design, with nearly identical power specifications to ATX and therefore fully compatible with power plugs as standard. these. The only difference in the standard is that SFX format sources (and standard mini ITX) do not require -5V rail (something that does not influence when we use modern hardware, since only ISA cards used it and in fact it was removed in the ATX 1.3 standard).
The difference between an SFX source and an ATX is, therefore, in terms of their dimensions. The standard says that a font in SFX format should measure 125 x 63.5 x 100 mm (width x height x depth) with a fan of 60 mm maximum diameter (so they could be even smaller), compared to the dimensions of ATX fonts measuring 150 x 86 x 140mm.
There is a version of SFX power supplies called SFX-L, whose dimensions are 125 x 63.5 x 130 mm and whose only objective is to be able to accommodate a 120 mm diameter fan.
Another of the peculiarities of this format of power supplies is that, as a general rule (because it depends on each manufacturer), the cables will be shorter (quite a bit, in fact) compared to those of an ATX source because, as we have told you They are initially designed for small form factor equipment and therefore will not need such long cables.
In which cases will you need a font of this format?
You will already assume that as a general rule, an SFX format source will rarely be able to be used on a PC with a “normal” ATX format box, although there are exceptions because many manufacturers include an accessory to be able to mount these sources in the hole of an ATX source , and as we said before, some also include long cables. However, this is not the norm.
The usual thing will be to use sources of this format when we are going to mount a small form factor PC, with a mini ITX board and, almost more importantly, a mini ITX box (due to the length of the cables). Many mini ITX boxes are designed to accommodate ATX format sources, but if we did, we would have a lot of cable length to spare, and that is why this format of power supplies comes into play (and for these boxes also manufacturers usually include the adapter).