Question about Intel ASUS P4C800-E Deluxe 875P Socket 478 DDR 400 ATX Motherboard 3-in-1 Combo (MP4C800EDLXCOMBO)

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PS_ON revertsto high as soon as +12V starts to appear on 2+2connector

Can't start system. If 12V2+2 connector plugged into MB, PS_ON goes back high right after going low. If 12V 2+2 not plugged in, power stays up, fans run, voltages check OK. All true with peripherals removed, only CPU and a couple HDDs to load the PS.
What conditions cause PS_ON logic to reject power when 12V2+2 connector is connected?


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Re: PS_ON revertsto high as soon as +12V starts to appear...

No need to get testy--no pun intended--I do appreciate your thoughts and help. What I want is to save the MoBo if I can. I'm sure it is deciding to turn off the PSU for a reason. I know the PSU will shut down if there is too much current draw, but I don't know what bad conditions the MoBo will use to shut down--probably voltage not reached in x msec, maybe overvoltage, and maybe in my case, the logic chip that ands the necessary conditions together and latches PS_On low is burnt. Today I'll try tracing the 12V from that connector on the board--probably doesn't serve much more than the CPU. Maybe I can find something.

Posted on Nov 24, 2007

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Re: PS_ON revertsto high as soon as +12V starts to appear...

Usually it is over-current that will make PS_ON go high. However, the opposite is true: if not enough load draw, PS_ON goes high and never goes low. Not exactly certain about link to 12V2+2 connector, although same theory may apply.

Posted on Nov 20, 2007

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Hi, Is the 24 pin power connection on the MB the only power connection to the supply? Or are there others? Thanks!

no there is a 12v plug across the board from the first power connector.
It is an optional plug that only serves to distribute the load into
a couple of other wires for heat dissipation, so they don't burn up.

Aug 13, 2011 | Biostar N68S3B GeForce 7025 Motherboard...

1 Answer

What arethe compatible components of this kind motherboard

CPU P5KPL-AM empty.jpg Valuable Intel G31 uATX solution with FSB overclocking 1600MHz!
- Intel® Core™2 Quad Ready
- Intel® 45nm CPU Ready
- FSB 1600(O.C.)/1333/1066/800 MHz
- Intel® G31/ICH7
- Dual channel DDR2 1066(O.C.)/800/667
- EZ Flash2 & CrashFree BIOS3
- 8 Channel High Definition Audio

Intel® Socket 775 Core™2 Quad/Core™2 Extreme/Core™2 Duo/Pentium® D/Pentium® 4/Celeron® E1000 Series and Celeron 400 Series Intel® Hyper-Threading Technology ready
*Refer to for Intel CPU support list
Chipset Intel® G31 Intel ICH7
Front Side Bus 1600*/1333/1066/800 MHz (*1600 is overclock speed) Memory 2 x DIMM, Max. 4 GB, DDR2 1066(O.C.)/800/667 Non-ECC,Un-buffered Memory
Dual Channel memory architecture
*Overclock speed
**Refer to or user manual for Memory QVL (Qualify Vendor List)
***When installing total memory of 4GB capacity or more, WindowsR 32-bit operation system may only recognize less than 3GB. Hence, a total installed memory of less than 3GB is recommended. Expansion Slots 1 x PCIe x16
1 x PCIe x1
2 x PCI
VGA Integrated Intel Graphics Media Accelerator (Intel® GMA 3100)
Max. resolution:2048x1536X32bpp, Horizontal:127.5KHz Vertical:85Hz Storage Southbridge
1 xUltraDMA 100/66/33
4 xSATA 3 Gb/s ports
LAN Realtek RTL8102EL 100/10 LAN
Audio VIA VT1708B 8 -Channel High-Definition Audio CODEC
Anti-Pop Function
Jack-detect & Multi-Streaming
Support S/PDIF Out connector USB 8 USB 2.0 ports (4 ports at mid-board, 4 ports at back panel) Overclocking Features SFS (Stepless Frequency Selection)
- FSB tuning from 200MHz up to 600MHz at 1MHz increment
Overclocking Protection
- ASUS C.P.R.(CPU Parameter Recall)
Special Features ASUS MyLogo 2
ASUS EZ Flash 2
ASUS CrashFree BIOS 3
Back Panel I/O Ports 1 x Parallel
1 x VGA
1 x PS/2 Keyboard
1 x PS/2 Mouse
1 x LAN(RJ45) port
4 x USB 2.0/1.1
1 x COM port
8 -Channel Audio I/O
Internal I/O Connectors 2 x USB connectors support additional 4 USB ports
1 x Floppy disk drive connector
1 x IDE connector
4 x SATA connectors
1 x internal speaker connector
1 x S/PDIF Out connector
1 x CPU/ Chassis/ Power Fan connector
1 x Front panel High Definition audio connector
1 x Chassis Intrusion connector
1 x CD audio in connector
24-pin EPS 12V Power connector
4-pin ATX 12V Power connector
1 x System Panel connector
BIOS 8 Mb Flash ROM
DMI 2.0
WfM 2.0
ACPI 2.0
Manageability WOL,PXE,RPL,WOR ,PME Wake Up Accessories User's manual
1 x UltraDMA 133/100/66 cable
1 x Floppy disk drive cable
1 x SATA cable
1 x SATA power cable
I/O Shield
Support Disc Drivers
Anti-virus software (OEM version)
ASUS Update
Form Factor uATX Form Factor
9.6 inch x8 inch ( 24.4 cm x 20.3 cm )
hope this helps

Jul 18, 2011 | ASUS P5KPL-AM - Motherboard - micro ATX -...

2 Answers

Just got mobo and set, fan doesn't start, mobo doesn't give any sound nothing moves....did basic removal of mem and unneccesry one by one and still nothing...

Power. Start with power.

1) Make sure the 24-pin ATX main power cable is plugged in tightly to the mobo.

Ensure that the lock on the male connector (Power cable) is snapped over the tab on the female connector. (Mobo)
Push down on each wire to ensure it's metal terminal connector, is plugged on tightly to each pin.

Looking at the middle photo you are looking at the Front of the connector.
Looking at the photo to the far right, you are looking at a side shot, and the back of the connector. The back is where the wires go in.

Each wire ends in a metal terminal connector.
The metal terminal connector is shaped like a tube, so that it will slide on the pins in the mobo's ATX main power connector.

The metal terminal connector also has two locking tabs. One on each side.

Sometimes there may be a problem with the locking tabs. The metal terminal connector is not tightly on the pin. May not even touch the pin. Check each wire in the 24-pin ATX main power cable's connector. Push in on each one.

Everything is fine so far?
Perform the diagnostic test to see if the problem is the Power On switch, or the Power Supply.

Use a jumper wire on the back of the 24-pin ATX main power cable's connector.
Touch the jumper wire from the Soft Power On wire to ANY Ground wire.

The Soft Power On wire is the Green wire.
ANY Black wire you see is a Ground wire.
(Soft Power On is also abbreviated as PS_ON)

The general type of jumper wire used is a paper clip.
Thin, and stiff, plus a conductor of electricity.
The paper clip is straightened out, then bent into a U-shape.

Black plastic electrical tape is wrapped around the middle of the U.
This area is for you to hold onto the jumper wire.

The 'legs' of the jumper wire, go down into the appropriate socket holes, in the BACK of the 24-pin ATX main power cable's connector.

One leg goes down into the socket hole with the Green wire (PS_ON), and the other leg goes down into a socket hole with ANY Black wire.

The paper clip goes down into the socket hole RIGHT NEXT TO THE EXISTING WIRE that is already present.
Slides down right next to the wire, and touches the metal terminal.

The metal terminal is pretty far down in there.
Ensure that the paper clip is touching both metal terminals on the Green wire, and any Black wire.

Power supply comes on? You have a bad Power On switch,

Power supply does Not come on? You have a bad Power Supply.

For additional questions please post in a Comment.

Jun 12, 2011 | Foxconn M61PMV Motherboard

2 Answers

Followed advice from "Ulangreg"...still have

It appears the motherboard is faulty. When the power supply is overloaded it will shut down. You have confirmed this by by removing the eatx connector and it powers up again.

Mar 02, 2011 | ASUS M2N32-SLI Deluxe/Wireless Edition ATX...

2 Answers

I've got a new Gigabyte Ga-M68Mt-D3 mobo paired with a cooler master 460 watt power supple. Cpu is Amd phenom II 3.2 ghz with 4 gig of DDR3 ram. I powered up the supply attached to my ATX power supply...

Most motherboards now have a 24-pin power supply connector. If you haven't already found a diagram showing the pinouts of the 20- and 24-pin power plugs, here's one borrowed from a handy site:


The two plugs are essentially the same, but the 24-pin version duplicates some voltages on the extra pins. The extra pins in the larger connector were meant to provide extra current paths for voltages that see heavy loads from newer processors and motherboard circuitry. Depending on how a motherboard is designed, it might work with a 20-pin plug connected (leaving pins 11, 12, 23 and 24 empty). But typically if the board has a 24-pin connector it needs the 24-pin power supply plug.

Most power supplies have a 20-pin plug with a separate 4-pin section that fastens to it for connection to a 24-pin mobo connector. It typically has one side designed to slide onto the end of the 20-pin plug, essentially turning it into the 24-pin version. This added plug does not have a retaining clamp on its side, so you can tell it from the the 4-pin CPU power plug. The wire colors are also different. For reference, here is the processor power plug, from the same website:

New motherboard specs call for the separate processor power connector for the same reason the extra pins were added to the power supply connector: to handle the high currents needed by increasingly faster CPUs.

When the motherboard has these connectors, you need to use them all to get everything working. Hope this helps. Thanks to for the diagrams, and thank you for using Fixya.


Nov 19, 2010 | Motherboards

2 Answers

System won't turn on but when i pushg down on one side of the power suply connectore the fan starts running but computer stioll won't turn on it used to boot up then opne day stopped

It sounds like you have a faulty connector - I would return the item under warranty. Otherwise, if it is out of warranty, you will have to source a new motherboard.


1 Answer

AA8 DuraMAX won't power up

if you are sure that the ps is ok replace the motherboard

Mar 21, 2009 | Abit AA8-DURAMAX Motherboard

2 Answers

MSI 1996 Motherboard: Power on Signal to PS staying high

check motherboard wire conector, make sure its not reversed

Dec 23, 2008 | Intel Motherboard

1 Answer

CPU does not start

Hi, have you tried removing all the cards (video, lan etc) and all power connectors to drives? Run only your mb. If problem persists then it is possible that there is a short in the mb since the psu auto protects and shutoff. You can also try removing the retaining screws of the mb and try running it completely off the back panel. Care should be taken to ensure that the back of the mb does not touch any metal part of the casing. You can try sliding in between a plastic folder or something. If psu still shuts off, then you it is most likely the mb is fried. Please let me know if this works out for you. Regards

Apr 09, 2007 | Intel D865GLC Motherboard

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