From ASRock's site, the User Manual for the motherboard states
"This mother-board also provides independent display controllers for DVI-D, D-Sub and HDMI to
support dual VGA output so that DVI-D, D-sub and HDMI can drive same or different
It only specifically mentions dual monitors. It makes no mention of three monitors.
Intel's, Question search has this to say
Most Intel graphics products can output to one or two displays at the same time and support several different multiple display configurations.
Starting with the 3rd Generation Intel® Core™ Processors with Intel® HD Graphics 4000/2500, three displays support may be possible depending on your computer's configuration. Check with your computer manufacturer if three displays are supported on your computer and which display combinations are supported."
I emailed ASRock's support.
Intel® HD Graphics 4000/2500 (or 3rd Generation Intel® HD Graphics controllers) are capable of three active video displays when the system uses two monitors connected through DisplayPort interfaces and a third video port (VGA, HDMI, DVI, etc.); or, when the system uses DisplayPort plus an additional video port (VGA, HDMI, DVI, etc.) and a third display connected through Wireless Display. Please keep in mind that USB would not count as a video interface for this purpose.
In some laptop systems, the system may also use the laptop’s display, is connected through an embedded DisplayPort (eDP), and then the second display is connected through DisplayPort or mini DisplayPort and a third monitor through an additional video interface.
is there a splitter/hub I can use to connect 3 DP1.1 monitors to a single DP1.1 port on the Intel HD Graphics 4000?
At this moment we do not have a list of tested cables that could be used for something like that. As you may know, these kind of devices may or may not work. Furthermore, in these kind of devices, the system may just recognize one of the displays as for Multi-monitor configurations the system needs to use separate video ports in the system, so splitting the signal from one single port, does not apply.