What if I don't use the 12V 4pin power connector that my mobo says I need plugged in?

JEDI

Lifer
Sep 25, 2001
30,160
3,300
126
i bought the nforce3-a/sempron 3100 combo from outpost.com deal.

fans spin but it wont bootup/post (nothing on screen)/turn off in my new case. that case has the regular power connector, plus the 12V 4pin one. Like THIS. the powersupply is a 500W noname brand (pwoermagic?).

i also tried it w/o the 12V connector. same thing.

the only thing i have plugged in is the cpu/cpu fan/memory/agp video.

i plugged the same system into my old ATX case that housed my k7s5a. it doesnt have the 12V connector. it boots up and posts by just using the regular 20pin power connector?! the powersupply is a 300W enermax.

so what is the 12v 4pin connector for? and what happens if i dont use it?
 

Krakn3Dfx

Platinum Member
Sep 29, 2000
2,969
1
81
I believe is't the connector for the 2nd leg of the dual +12v rail that a lot of PSUs offer these days, so it would take some of the work away from the primary +12v rail, but I could be way off on that.

I know a few people who never plugged into the 4 pin connector until I mentioned it to them, and they never had any problems, but I do hear about stability issues online with some people. I guess it probably comes down to how much stress your PSU is under to power the components in your PC.
 

torpid

Lifer
Sep 14, 2003
11,631
11
76
You had the power switch lead connected to the motherboard in the new case, right?
 

JEDI

Lifer
Sep 25, 2001
30,160
3,300
126
Originally posted by: torpid
You had the power switch lead connected to the motherboard in the new case, right?

yup..edited my msg to say cpu fan spins, but nothing on the screen. video card works since it's from my main system.
 

ojon

Junior Member
Feb 1, 2006
1
0
0
Originally posted by: Krakn3Dfx
I believe is't the connector for the 2nd leg of the dual +12v rail that a lot of PSUs offer these days, so it would take some of the work away from the primary +12v rail, but I could be way off on that.

I know a few people who never plugged into the 4 pin connector until I mentioned it to them, and they never had any problems, but I do hear about stability issues online with some people. I guess it probably comes down to how much stress your PSU is under to power the components in your PC.

Krakn3Dfx:

The second of two rails incorporated into a 24 pin connector is not the usual 4 pin 12V connector. The second rail is the extra 4 pins that make up the connector. This has nothing to do with the separate 4 pin 12V connector. I run a DFI Nforce 4 motherboard that makes use of both connectors along with a regular molex connector and a floppy type connector. They're all plugged in and said to provide increased power stability.
But both V12-1 and V12-2 are present in the 24 pin connector.

ojon
 

Jhhnn

IN MEMORIAM
Nov 11, 1999
62,365
14,681
136
Both the 24 pin connector and the 4 pin connector were adopted to increase power handling capabilities- each pin/socket interface only has a certain current handling capability. So, while everything may seem to work just fine w/o them, even mild overheating at the connection can cause cumulative damage over time, resulting in failure...

As for diagnotics of the boot problem, try booting with just the cpu installed- no memory. If the cpu is good, then the board should just give a continuous beep, indicating no memory... if the cpu or board is defective, the symptom won't change from what you have now...
 

Zap

Elite Member
Oct 13, 1999
22,377
2
81
Let me get this straight... the OP said the same mobo/CPU/HSF/RAM/video works on his Enermax PSU but not on his generic PSU? I can think of four possibilities...

1) The generic PSU is dead.

2) The generic PSU isn't putting out clean enough power for the board to power up (unlikely, usually just causes instability).

3) The generic PSU is incompatible with the motherboard (can happen, many reports of Antec Neo HE being incompatible with some Asus boards).

4) The case that the generic PSU is in has something that shorts out the motherboard when it is bolted in (an assumption that the board was "installed" and not just on a non-conductive test bench).

As for the 12v connector, some boards work fine regardless (indeed some boards don't even have the plug). Some boards seem to work fine but may exhibit some instability. Some boards won't power up without it.