I've got a Dell Vostro 470 with an AMD Radion HD 7570 graphics card. On the back of my computer, I see a VDI port (looks like it is added as extra) and a VGA port. The primary monitor that I bought with the desktop pc is attached to the DVI port.

Now I've got another ACER AL1721 monitor that I want to attach as a second monitor, so I plug it in into the VGA PORT but nothing happens ("no signal"). The screen resolution window doesn't show a second monitor nor does the Catalyst Control Center.

How can I make this second monitor work/recognized.

What I have tried

  1. Click 'detect' on the screen resolution window and Catalyst Control Center
  2. Tried the second monitor on a laptop, works
  3. Restarting computer
  4. Updating AMD driver (not sure if I updated correctly, manually searched for an update)
  5. Went into my BIOS & turned on 'Intel Multi-Display'

3 Answers 3


This is because you are plugging your second monitor into the onboard graphics and not into your video card.

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On the back of your computer where you have your DVI connected is the graphics card (green square). You have your second monitor plugged into the motherboard (red square).

In order to plug in your second monitor as VGA, you will need a second DVI port (most graphics cards have two, it should be next to the DVI you are using) and a VGA to DVI adapter.

A second solution is to get a DVI Y splitter which will take two DVI inputs and turn them into one DMS-59 input which is supported by most modern video cards.

  • There's only a HDMI port next to it. Where would you localize the DMS-59 input then ? Can't find anything like that when I google an image of it. Commented Jul 27, 2013 at 20:52
  • @SergeMorel Then you may need to go with the second option and pick up a DVI Y Splitter. This will let you use one DVI port for two monitors. Of course this also means getting a VGA to DVI adapter for your second monitor. If your second monitor supports DVI though, you could just grab a DVI cable and use that, but either way you'll need a splitter. Commented Jul 27, 2013 at 20:55
  • It supports DVI (second monitor), guess I'll have to go buy a DVI Y Splitter. I can still have an extended monitor with this right ? Or will it just be a duplicate ? Commented Jul 27, 2013 at 21:31
  • It should support both extended and duplicate. If you wanted you could even connect your DVI monitor via HDMI and then use the VGA to DVI adapter for the second. Not sure if that is any cheaper, but it would probably save you the hassle of splitters if you wanted to go that route. Commented Jul 27, 2013 at 23:21
  • 1
    I just bought myself a HDMI to DVI cable to connect the second monitor to the HDMI port on the computer's back. Commented Aug 4, 2013 at 13:37

This was driving me up the wall. Like the first answer, I have a DVI port connected to the graphics card, and my VGA where it shows...connected to the motherboard.

I also noticed I have a DisplayPort right next to my DVI port. I was planning on getting a DisplayPort to DVI port adapter and an extra DVI cable.

I decided to tinker with some other stuff.

I shut down my system and saw the boot menu. I opened that and went into some different tabs, where I discovered the Device Settings. In that "Integrated Graphics" was turned off. So I turned that on just to see if anything would change. I don't think I changed anything else. But I'm not going back to try to repeat what I did.

My computer started and, much to my surprise, my 3rd monitor came on. Also, it finally showed up in my device manager as a 3rd PnP Monitor.

Take a look at the boot menu and see if you can check that setting. It might work for you like it did for me.

I'm on a pretty old HP 8300 small form factor.


With the serial port unplugged, do the following:

  1. Go to control panel -> hardware and sound -> connect to projector Your get 4 options, chose the last one which is "connect to projector only"
  2. Now plug in the serial port cable into your laptop.
  3. Both displays go dark, Wait for a few seconds.
  4. Built in display lights up, saying that project could not be detected.
  5. Leave the serial port plugged in. You have now solved 75% of the problem.
  6. With the serial port cable for digital display plugged in, click with 3rd mouse button on the built in display screen.
  7. Chose graphic options --> output to --> clone displays.
  8. Both displays will get cloned. Now try the extend display option.
  9. output to --> extend display --> built in display + digital display
  10. You have what you need.

Hope this helps

  • Technically I believe VGA/DB-15 is a serial communication, but the plug/cable is usually referred to as I just stated. The term 'serial port' most commonly referes to a DE-9 (now DB-9) or 9 pin cable/port not used often these days. Old gaming periphs/joysticks used this among other things.
    – Cand3r
    Commented Mar 7, 2016 at 19:00

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