24 pin power cable?

[Mark Kaine]

So I'm a bit confused here, if my power cable uses all 24 pins I logically should also connect both plugs on the other end of the cable into the PSU, right? 

 

I'm just asking because in the manual of this Bequiet straight power 11 it explicitly tells you to plug in both connectors into the *motherboard* (duh) if motherboard has 24 connection... but nothing about what goes into the PSU side, which is really stupid considering this is a manual that's supposed to tell you what to do... 

 

 

I'm also wondering how semi modular PSUs handle this since you don't have the option to *not* plug in a second plug into the PSU... 

 

I*hate* fully modular power supplies lol, the manual of my pure power semi modular is 10 times better... with fully modular they just expect you to know every thing, trial and error style...

[Hairless Monkey Boy]

7 minutes ago, Mark Kaine said:

So I'm a bit confused here, if my power cable uses all 24 pins I logically should also connect both plugs on the other end of the cable into the PSU, right? 

Whether or not you use 20 pins or 20+4 pins on the motherboard side, you should always fully connect all of the connectors on the other side of the cable into the PSU.

[minibois]

I'm not 100% sure what you're asking, but if the question is "Why does the 24 pin cable on my motherboard side not match the PSU side of the cable?", it's because these cables don't have to match on the PSU side. They can often use more cables, which merge together or split off, etc.

[Mark Kaine]

1 minute ago, HairlessMonkeyBoy said:

Whether or not you use 20 pins or 20+4 pins, you should fully connect all of the connectors on the other side of the cable into the PSU.

Ok, I figured, since as said you don't even have this option with semi modular, thanks. 

 

(now I'm wondering what happens if you *dont* plug in that second cable and why they're even split to begin with tho...) 

 

[mariushm]

For backwards compatibility, some power supplies have a 24 pin connector that can be split into 20 + 4 - you plug both connectors into the 24pin header in this case.

 

The ATX standard originally had only 20 pins and had a lot of 3.3v and 5v wires, because almost all components in computers were powered from 5v or less ... all except fans and hard drive motors. So in the 20 pin connector, there's only ONE 12v wire, for around 100 watts of power maximum.

The 4 pin segment was added to provide an extra wire for each 3.3v, 5v and 12v, when the transition was made to power processors from the 12v input. At that time they also invented the CPU 4 pin power connector, and now the EPS (cpu 8 pin) is used, imported from server motherboards.

 

The side going into the power supply is not standardized, so each manufacturer can use their own header or headers - sometimes it makes sense to split the 24pin into 2 x 12 for example, or 1x10 + 1 x16 , in case the psu side has extra wires (voltage sense wires for example, used to measure the voltages at the motherboard header)

[Mark Kaine]

2 minutes ago, minibois said:

I'm not 100% sure what you're asking, but if the question is "Why does the 24 pin cable on my motherboard side not match the PSU side of the cable?", it's because these cables don't have to match on the PSU side. They can often use more cables, which merge together or split off, etc.

no, see above, I'm more asking why is the cable split if you need to use both plugs anyway on the PSU side, and why isn't this better or rather at all described in the manual... 

[minibois]

5 minutes ago, Mark Kaine said:

no, see above, I'm more asking why is the cable split if you need to use both plugs anyway on the PSU side, and why isn't this better or rather at all described in the manual... 

The reason why they do this I'd have to guess has to do with parts availability.

The Be Quiet Straight Power 11 has - for the 24 pin ATX connector - on the PSU side a 10x2 pin (20 pin) connector and a 4x2 (8 pin) connector. Those are quite common connectors, so it's probably a lot easier for them to get those, rather than a 14x2 connector.

 

Why it's not explicitly described in the manual?

I have no way to word this very kindly, but I'd have to assume when people build a system and are presented with a cable that goes to your motherboard, you'd look at the two ends of the cable and plug it into the two connectors that fit these cables, which are labeled "MB". Kind of like the whole "LEGO for adults!" premise of building PC's.

17 minutes ago, Mark Kaine said:

(now I'm wondering what happens if you *dont* plug in that second cable and why they're even split to begin with tho...) 

probably the same as what happens when you don't plug in any type of cable. Irregularities and instabilities start to pop up.