ATX Form factor Introduced (1995/1996)

[chrisNova777]

https://en.wikipedia.org/wiki/ATX#Original_ATX

ATX, introduced in late 1995, defined three types of power connectors:

4-pin "Molex connector" — transferred directly from AT standard: +5 V and +12 V for P-ATA hard disks, CD-ROMs, 5.25 inch floppy drives and other peripherals.[16]
4-pin Berg floppy connector — transferred directly from AT standard: +5 V and +12 V for 3.5 inch floppy drives and other peripherals.[17]
20-pin Molex Mini-fit Jr. main motherboard connector — new to the ATX standard.
A supplemental 6-pin AUX connector providing additional 3.3 V and 5 V supplies to the motherboard, if needed. This was used to power the CPU in motherboards with CPU voltage regulator modules which required 3.3 volt and/or 5 volt rails and could not get enough power through the regular 20-pin header.
The power distribution specification defined that most of the PSU's power should be provided on 5 V and 3.3 V rails, because most of the electronic components (CPU, RAM, chipset, PCI, AGP and ISA cards) used 5 V or 3.3 V for power supply. The 12 V rail was only used by fans and motors of peripheral devices (HDD, FDD, CD-ROM, etc.)

ATX form factor was first introduced in late 1995. but really didnt see mainstream adoption untill early 1997. but there were a few models between early 96 + late 96.