It's interesting is this. I read "24 pin" and thought "huh". Did a bit of reading and things are changing - again. Like it isn't a complicated mess as it is. So now there's BTX, which has compatibility with ATX components but AGP has gone out the window
I would guess that the 4 pin is there for older (ATX) PSUs that have the 20 pin and 4 pin connectors. Newer PSUs will have just the 24 pin connector, which is (again, guessing) the merging of the 20 and 4 pin connectors. Question is "why". Geeks always have to fiddle
