i just bought a new PSU with 24pin (not 20+4) and a mobo that has a 20pin connector.
i've done some research and i realise that the last 4 pins are not used, yet there are models out there which are designed to be able to detach the last 4 pins.
so is it safe to assume that IF my motherboard allows me to plug in the 24-pin connector, and leave the last 4 pins dangling, it will work?
(i have compared the 24pin connector with a 20pin connector and color codes of the wires are the same. i plugged in the 24 pin connector into the 20pin mobo and i made sure the colors match the 20pin connector)
Yes, that is true. The first 20 pins are wired the same way. I doubt however that the MB will allow the last 4 pins to dangle. You can either try to find an adapter, detach the last 4 pins like you mention, and if that option is not available then you'll likely need a new PSU.
i noticed that the 20-pin psu are the same output voltages with 24-pin psu (regardless of color) EXCept pin #15 which is -4.93Vdc.
24-pin psu @pin 15 has no output voltage/no terminal. so, thats why i confused if this is safe to use the 24-pin psu to the 20-pin mobo