Hi! This thread is very useful and helpful for me and maybe for persons who try to set up triple display monitors on Intel HD 4000 Graphics.
Thank you Erik.Andersson and kevin_intel for useful information!
I use the HP 2570p laptop (within Intel core i5 Ivy Bridge and Intel HD 4000 Graphics) with Windows 7 Enterprise 32 bit. (I wonder why 32 bit OS selected by the IT administrative section of my company.)
Because I also use its docking station, there are three available display connectors, a VGA and a display port on the docking station and another display port on the right hand of the laptop.
I want 3 or 4 display monitors in extended mode in my job.
This laptop does not have an Intel® Wireless Display (Intel® WiDi) module nor an Embedded DisplayPort1 (eDP) but LVDS, so I have to choose the first condition, says "If two of the displays are DisplayPort monitors."
Sadly, I just have old LCD monitors that have only single VGA connector or double (VGA and DVI) but no DisplayPort. Using two DP to DVI active adaptor, I can get the triple display monitors working condition, that is following,
DPtoDVI(active) - DPtoDVI(active) - VGA, and
DPtoDVI(active) - DPtoDVI(active) – LVDS (monitor in laptops).
If exchanging each DPtoDVI active adaptor to its passive adapter, that just cause to get the decreased the maximum number of monitors to the double. Thus DVI does not seem to compare to DisplayPort, although both are digital signal transports, DVI connection seems to need an additional clock generator in an active adaptor.
First, I got the information Intel GPU core has only 2 pixel clocks and 2 DisplayPorts can share one pixel clock, and the other one can use for VGA or LVDS in somewhere community board. I thought that it needed total three signal transports contain two digital signal transports and one analog VGA transport, so I expect DP to DVI passive adaptors are enough to work it, but these were not working enough.
To tell the truth, I did not know there ware the kinds of DP to DVI adaptor, active and passive. What active?
When I was searching it in Google, I understood there was a clock generator chip in "active" adaptor and passive one did not have it. These of recent products looked like the same figures, only difference was a chip inside which could not be seen. I bought "active" adaptors from Amazon, but I had even understood it really "active", since I had seen all the devices connected to work it out perfectly. Watching it well, there are only three differences I found, gold-courting in connection port part, little short length of the cable, inside shape of the connection cover, it seems no relative to work or not.
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I do not know which a clock generator in active adaptor is equal to a GPU core pixel clock, or not. Simply counting the number of clocks is 4 that more than 3 monitors. Does it mean "1 clock remains"? Or the clock generator is not a pixel clock and that can just help it?
Because I am not an IT specialist, so I may not understand it soon. (^^;)