ASUS P5Q SE2 Serial Connector Pinout

I had to search a while to find this pinout, so I might as well post it so someone else can find it —  although I have a feeling that I’ll be the one that needs it again.

Link to original forum post that pointed me in the right direction

Link to PC Cables page with correct connector

Copy of correct pinout

DB-9	IDC-10
Pin 1 	Pin 1
Pin 2	Pin 2
Pin 3 	Pin 3
Pin 4	Pin 4
Pin 5 	Pin 5
Pin 6	Pin 6
Pin 7 	Pin 7
Pin 8	Pin 8
Pin 9 	Pin 9

UPDATE: (2009-07-22)

The pin-out for the serial connector on the motherboard is incorrect in the some manuals.  In fact it is incorrect in the latest English version dated September 2008 on the ASUS website.  The correct pin-out is:

--- ---

Thanks to Andreas for his help establishing this.

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  1. Wait, wait, wait! Is the IDC-connector on the P5Q upside down??

    I have 4 pins in the upper row and 5 in the lower row.

    Is it

    |2468 |


  2. Looking at the manual the pin-out for the serial port is:

    Looking at that, the pin-out in the post connects pin 9 to pin 9 which looks to actually be a no connect.

    But all this is immaterial if you use a IDC plug with a 10 pin ribbon cable. If you don’t have one and are wiring with individual wires take a look at how the pins are connected on an IDE or FDD cable. All that really matters is that you connect pin one – the red marked wire to pin 1 of the DB-9 and take your pin count from the ribbon cable. It all should work itself out.

  3. I just had a look at the manual on page 2-29 (hope you got the same manual in the US like I have it here in Germany). In the Image you can see “PIN 1” at the lower left. And the connector on the mainboard has a gap on the lower side of the frame.

    Looking at the picture on you can see the “nose” that fits in that gap on TOP of the IDC plug and pin 1 at the upper left.


    So I still think that the connector on the mainboard is just turned upside down:

    |– –|

  4. I downloaded the manual from Asus:

    It has the same pin-out as my manual does. Thinking about it, you’d think the key (missing) pin would be pin 10. I didn’t notice that the PC Cables diagram has the pins labeled like your diagram too. I think you and PC cables have the right pin-out.

    Tell you what, I can’t do it right now, but later today I’ll shut my box down and tell you which pin is pin 1 on my cable.


    I’ve been burned by companies putting the wrong pin-out in the manual before. I can’t remember the company, but the manual I had had the wrong pin-out for the USB ports and I blew them out. Only then did I go to the website to get the latest manual and find out they had corrected the pinout.

  5. I shut down my computer and looked at the cable. The way it is wired pin one connects to the lower left. Andreas is right! Both my manual and the English manual on the ASUS website are incorrect.

    I’m going to update the post to show this information.

    It’s worth noting that this is a serial port, so wiring it incorrectly probably won’t hurt anything — not like a USB port that also provides power.

  6. 1 more this helped. I happened to have an adapter cable laying around, but it didn’t work. was pinned 123… across instead of 135… as described above. rewired it, and works great! Thanks a bunch!!! -ASUS M4A79XTD EVO manual does not even have pinouts.

  7. @Steve:

    I can’t verify exactly what the eBay seller means by straight and reverse wiring, but straight wired usually means pin 1 goes to pin 1, pin 2 to pin 2, etc…

    When they say reverse, I suspect they mean a cable wired like the following example:

    Worst case scenario, you get the wrong cable, you usually can pop the individual pins out of the IDC-10 connector and re-arrange them.

    Hope that helps.

  8. Mister, you’re a genius. 2 years stucked with a problematic USB COM port!!!….. Don’t lose the way, Pin 1 with Pin1, Pin2 with Pin2, etc. That’s the solution!!!…. Millions of thanx!!!

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