I have a (old) computer that I am trying to use, just for giggles. It has a 9-pin (RS-232) output for the monitor (marked 10101). Can I connect it to my VGA monitor using an adapter?


Thanks for you input guys. But the serial port has both, the 10101 and rectangular symbols next to it!

enter image description here

What does this mean?

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    If you can attach it :))) (No, seriously, .... just - no!) – Rook Feb 5 '12 at 22:44
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    Being labelled "10101" indicates that it's a serial port, not a monitor port. – Hand-E-Food Feb 5 '12 at 22:46
  • What is the make and model of PC? – RedGrittyBrick Feb 5 '12 at 23:26
  • @RedGrittyBrick There is no label but the mother board is Asus P4C800 – Ram Feb 5 '12 at 23:48

No it will not work with a VGA monitor.

If it is specifically marked as RS-232 (or with a string of one’s and zero’s), then it is a serial port for things like serial mice.

If it on the other hand, it is marked with Mon. or a rectangle, then it is a DE-9 connector for CGA or EGA monitors.

VGA monitors use a special D-sub 15-pin connector (DE-15F) and cannot be connected even with an adapter because the pinouts are completely different (because VGA is analog and works very differently from the older, digital CGA and EGA standards). You could try looking for a converter, but I for one have not seen or heard of any such thing, and would imagine it would be expensive anyway.

Your best bet is to check the local classifieds (especially online ones such as Kijiji or eBay Classified) to see if anyone nearby has a 9-pin monitor collecting dust in the closet. You could also put your own ad specifically asking for one.


Seeing your photo and the model of the motherboard, it is most definitely a serial port. The P4C800 does not have a 9-pin monitor connector (or even onboard VGA).

What you see is a generic bezel not specific to that motherboard. Cases used to come with several bezels of common variations, but because these days, motherboard backplanes come in a wide variety, they don’t and instead, motherboards come with a bezel specific to the board that can be snapped into a case. The one you see has both icons because it can be used for different motherboards and on some, instead of a serial port, there is a 15-pin VGA connector there (which has the same physical dimensions of a 9-pin serial port).

In summary, no, a serial port is not a video port and there is no way to use a monitor of any kind with it (even a 9-pin monitor, let alone 15-pin one). Since it does not have onboard video, you will need to install a video-card.

enter image description here

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  • Wait, the older ports from before VGA were digital? Why in the world did we ever switch to analog - just because they didn't want to include DAC's in our CRT's? – BlueRaja - Danny Pflughoeft Feb 6 '12 at 4:46
  • > Wait, the older ports from before VGA were digital? Yes; yes they were. > Why in the world did we ever switch to analog - just because they didn't want to include DAC's in our CRT's? I don’t think that was the reason (what benefit would there be overall? it just moves the DAC to the video card). I think I have read about the reason at some point in the past, but cannot remember it now. Off the top of my head though, I think it had something to do with the increased resolution and/or color depth and/or refresh rate. – Synetech Feb 6 '12 at 4:52
  • The monitors themselves were effectively analog for CGA & EGA; it's just that the graphics card would only output "all the way on" or "all the way off" for each color channel (with a dedicated wire for "intensity"). VGA added intermediate voltages to represent more color depth, dropped "intensity", added some ground wires to reduce noise, but the monitors worked very similarly. – Sydius Aug 4 at 21:42

A 9 pin serial port is a communication port and CANNOT be used for a monitor. VGA is 15 pins and 15 pins only. Is what you have perhaps a DE-9 (also known as serial) connector? I do not believe there is an existing adapter for that type of conversion.

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    > Though what I think you have is really a serial and not a DE-9. Serial (RS-232) is DE-9. – Synetech Jun 28 '12 at 5:47
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    Honestly I have no idea why I wrote that, I know its the same. i must have meant to say serial and not VGA. – Paperlantern Aug 8 '12 at 19:25

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