I've searched for ages but can't find any answer to a basic question: why is it not possible to have both the integrated graphics processor in the i3/i5 as well as a discrete graphics card (PCIe 16x) both working simultaneously for multiple monitor display?
Do they share common processor components, clash on the bus, or what exactly?
Allan's answer tells me HOW the graphics are mutually exclusive, i.e. the system is designed to disable the one, but it still doesn't answer my question, which is WHY this is done? Is there a technical reason why they can't run in parallel, or do manufacturers just assume nobody will want to?
It's not that simple. I've heard the next gen might be able to do that, but such feature requires cooperation with not only the motherboard vendors but the graphics card vendors that make the add-on cards. There's two main ones, AMD and Nvidia so they'll have to work to get it working seperately. Then after that they'll have to release a driver that cooperates with the add-on graphics card driver, which requires things like validation.
In the Tech notes it states specifically if you install a PCI Express x16 card the on board graphics are disabled automatically, along with the HDMI output. Thats the way the Mother Board was designed. There is 3 other options for a Dual-Monitor set ups. The first way is to take advantage of Intels Dual-Monitor set up is you have to use the on board graphics with either the CRT connector or the DVI-D connector and then you can use a HDMI cable to a TV set that has HDMI input which gives you Dual Monitors. A second way is to invest in a PCI Express x16 with Dual out puts. I'm using a eGeForce 8600GTS 256MB with Dual DVI out puts "Works perfectally". The third way would be to use the two PCI Express X1 slots which would once again give you Dual monitor out puts but you would have a investment of two graphics cards. I would recemond you check the vendor of the graphics card you are interested in and see the FAQ'S for that vendor to check compatibaly for your Mother Board with Intels chip set. Of course you will need the latest drivers for your graphics card to make this work correctly. And finally I will be checking myyself for a different graphics cards so I can use the two PCI Express X1 slots the Mother Board provides which once again gives you two connections for two monitors. I'm using XP Pro SP2 with all of the updates to SP3 from windows and eGeForce, and I have no problems. The box my Mother Board came in states Dual Independent display for procesors with Intels Graphics Technology.My Mother Booard is the DH55HC and I have a i5-650 Dual-Core Processor. The LGA1156 Scoket for this Mother Board supports many different Processors as long as they are LGA1156 pagkage socket. I have the i5-650. Other processors supported by this board are the is and the i7 and i3. I can't wait to check out the newer PCI Express x1 sockets, which I will put graphics cards in both of those sockets. So I have given you three different ways to get a dual monitor set up.