Well i did some testing with mixed results. Anyway of course what you can do will be dependant on your machine capabilites anyway.
I have a Dell XPS L502X (i7-2720 8GB with a GeForce GT540M dedicated graphics card)
It has an HDMI output port and a Mini-Display port on the back of it.
Unfortunately the only DisplayPort cable I have at work is not the mini version
so I couldn't test my machine out.
this guy has the pretty much the same unit and the way i read it seemed to work out for him when he connected the HDMI and the MiniDP separately.
Dell L502X with two external monitors#
Now I'm tempted to get a MiniDP adapter for 10 bucks on ebay just to try it out.
Not much point as this a work machine so I can't do any photo editing on it anyway.
I tried the same thing on another guys Dell Studio XPS 16 (about 3 y.o.) as he had an HDMI and a normal size display port.
We could only get 2 displays at once to work correctly. A 3rd dispay was recognised but as soon as we tried to extend the desktop onto it or duplicate it, one of the other displays swithced off.
I also tried it with my own personal Toshiba Portege 13.3" R835 (i5-2435 6GB with integrated graphics only).
This machine has only got crappy little 1366x768 display so I use it at home with a Dell U2312HM which is a lot better.
The Toshiba has an HDMI and a 15pin VGA analog output, so I tried connecting both of these at the same time to 2 Dell Displays a U2311H and a U2312HM
I could not get it to display on the two 23" displays plus the Laptop LCD at the same time with any combination of extending or duplicating screens (1 screen of the 3 was always blank).
The 3rd screen was identified and recognised but after trying to display on it, one of the others dropped out.
The best I could do was to have the 23" HDMI as the main display and extending onto the other 23" on VGA . Both runing at 1920 x 1080 resolution. (still, this did look pretty good to me with plenty of "real estate")