The AT power supply and the ATX power supply are the two core generations of PC power supplies in the history of PC power supply development. The main differences lie in the interface, power supply method, and shutdown logic. They are fully compatible with different generations of computer motherboards. Now, the AT power supply has been completely phased out. The ATX is the mainstream for home/competitive PC. The AT power supply: an antique standard, introduced in 1984, is compatible with early AT/ATX motherboards (such as Pentium 2, the first generation of Celeron before that), and was mainly used in old-fashioned desktop computers from the 1990s to the early 2000s. Now, it only exists in second-hand and industrial old equipment. 

ATX power supply: Introduced by Intel in 1995, it is an alternative to the AT power supply. It is compatible with all modern motherboards (ATX, MATX, ITX, etc.), applicable from home office machines to high-end gaming computers and workstations, covering all scenarios. Currently, it is the absolute mainstream. 

Incompatible interconnection: The AT power supply cannot be used on modern ATX motherboards (interface mismatch), and the ATX power supply cannot be used on old-style AT motherboards. Forcible modification will damage the hardware. 

Practical operation differences: After the AT power supply is turned on, it must be shut down by pressing the power button on the case; it cannot be shut down through the system (Windows). The ATX power supply supports "system shutdown", and both pressing the case button and clicking the system shutdown can achieve it, which is suitable for current usage habits. 

Reason for elimination: The AT power supply lacks anti-misuse features, no comprehensive protection, does not support modern hardware, and its power consumption / efficiency is not up to par. It was completely discontinued by manufacturers after 2005. Now, it is impossible to purchase a brand-new AT power supply. When assembling a new computer (especially an e-sports console), there is no need to consider the AT power supply. Just choose the ATX specification (select the power based on the CPU + graphics card power consumption, and select modularization and 80Plus certification according to your needs). 

The above explains the differences between AT and ATX power supplies. I hope this information is helpful to you.