How do i know if my PSU is ATX?

[Joseph Locicero]

I have a dell inspiron 3847 and im not sure if the PSU is atx..how would i know?

 

[avarice]

1) It should say so on the side of the PSU somewhere.
2) It will have a 24 Pin connector for the MB
3) Find the serial number, google the manufacturer/serial # and read the details.

 

[zenx]

It is
ATX is a standard, a collection of specifications for motherboards / cases and PSU-s.. basically refers to standard sizing / electrical parameters / etc so they fit each-other.
Nowdays just about any desktop PSU fits the ATX standard, since the main difference between AT and ATX is that AT psu-s used to be wired directly to the power button.. so you would turn off the psu once the operating system was shut down.. (remember the old days when you had the DOS message that it is safe to turn off your computer?). So just about every computer that powers off completely when you use a shut down function from the OS has an ATX psu..
Also the standard for them is one 20-24 pin connector to power the motherboard and a 4 pin connector for the CPU.

EDIT: I'm updating this to be less 'confusing'.. So the ATX standard was developed in 1995 so basically everything made after that has an ATX psu... and that's about it for PSU-s (there is no microATX and stuff, those are for cases and motherboards and refer to their sizes only, the connectors still fit).