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Why does my laptop only connect to one external monitor at a time?

Posted on 2014-08-10
Medium Priority
Last Modified: 2014-08-10

I wanted to have multiple screens for when I use my laptop, so I took my Lenovo Ideapad P500 and connected it to my TV with an HDMI cable. I got it to project a second screen to my TV and could drag programs from my laptop screen to my TV and vice versa. So then I used the VGA port on my laptop to connect to a regular computer monitor; however, there was no image and I could not get a third screen on my external monitor. In my computers settings, I found out that it recognized the external monitor as a display but it would not project to it. I eventually found out that I could take out the TV HDMI connection and then get a display on the external monitor but when I plugged the HDMI back in, it would recognize the TV as a monitor but not project a third screen to it.

Why can't I get both of my external monitors, along with my regular laptop monitor, to project 3 different screens?

Question by:forwiw2day
LVL 63

Accepted Solution

☠ MASQ ☠ earned 1000 total points
ID: 40251920
It's a straightforward hardware limitation of your graphics chipset, you can display up to two outputs at any time but one of those is built-in.  Most entry level graphics cards for desktops behave the same way, some even having three outputs but only two of them can be used concurrently.

If you want identical external displays you could use a splitter to get a further output but this is just a clone of the other external.
LVL 57

Assisted Solution

by:Joe Winograd, EE MVE 2015&2016
Joe Winograd, EE MVE 2015&2016 earned 1000 total points
ID: 40251941
I don't know about your Lenovo, but I have an HP 8460w laptop in an HP advanced docking station and it supports three monitors, but only after I figured out the trick — when I first tried it, I could get only two monitors working. The solution was to get an active adapter, not passive. I first purchased this DisplayPort (male) to DVI (female) Active Adapter for one office:

It works perfectly. I now have three monitors working where before only two of the three worked at a time. For a second office where I was having the same issue, I purchased this DisplayPort (male) to HDMI (female) Active Adapter:

This also works perfectly and I now have three monitors working at that office, too.

The first two monitors are connected to the dock via DisplayPort and DVI. I'm driving both at 1920x1200. The third monitor may be either the laptop display or an external VGA monitor.

The StarTech website has a good explanation of why you need an active adapter instead of passive to get the three monitors working:

Also, the AMD website has this nice description (and other excellent material) of the basic requirements for connecting multiple displays:
Connecting multiple monitors for AMD Eyefinity technology couldn’t be simpler. There are four easy rules to remember:

1. The first two monitors can connect to the graphics card with any display output on your product: HDMI, VGA, DVI or DisplayPort.

2. The third (or greater) display must be connected to the graphics card via DisplayPort.

3. If your monitor does not have a DisplayPort connection, you will need an inexpensive active DisplayPort adapter for it. DVI to DP adapters can be had for less than $30 USD.

4. Every family of GPUs supports a different maximum number of displays.
Of course, the computer must have AMD Eyefinity technology for this solution. Regards, Joe
LVL 19

Expert Comment

ID: 40251953
as writren above, it could be and probably is limitation of your graphic adapter (to have 3 different video outputs).
anyway I guess you can have 2 external monitors connected - just connect TV (HDMI) and desktop monitor (VGA) and do not display anything on laptop´s built-in display (e.g. set in Power settings to do nothing when you close a laptop lid so when you close it output will go to TV and desktop monitor - if you set output to 2 monitors (clone or extended)
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Author Closing Comment

ID: 40251970
Thanks Experts.  Don't have a DVI monitor to try the adapter solutions.
LVL 57

Expert Comment

by:Joe Winograd, EE MVE 2015&2016
ID: 40251972
You're welcome. Btw, it doesn't have to be a DVI monitor — could be DisplayPort or HDMI. Regards, Joe

Author Comment

ID: 40251974
sorry, I meant DVI port on laptop, Thanks
LVL 57

Expert Comment

by:Joe Winograd, EE MVE 2015&2016
ID: 40251996
It's probably not going to work just on the laptop. You'll likely need a docking station and even then it has to be capable of it. I could not get the laptop screen (of an HP 2540p) to work simultaneously with both a DisplayPort and VGA monitor, as discussed in this article:


But I did get the laptop screen (of an HP 8460w) to work simultaneously with two external monitors when the laptop was on an HP advanced docking station, as discussed in this thread. Regards, Joe

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