What is the difference between auto and onboard/card on the dell optiplex 960? The description is very lacking. As the name suggests for auto, if I do not have a video card inside, it will still use the integrated but for onboard/card it seems to be the same too. Also, it seems as though my 128 mb of my ram is dedicated to the graphcis card and either selection will not disable it. I upgraded the bios to A10 as well.
If set to Auto, if you have two graphic cards but only one monitor, the system will be smart enough to know which graphics card the monitor is plugged into and you will see your display.
Onboard/Card, on the other hand, will actually disable your integrated graphics card and on only the dedicated graphics card will work on your machine. Even if you have the monitor connected to the integrated graphics port, it will not have any displays.
Depending on your system, setting it to Auto may also allow you to extend the maximum number of monitors connected. For example, if your IG (integrated graphics) supports one VGA and your DG (dedicated graphics) supports two monitors via VGA and DVI then you may essentially be able to run three monitors total (1 on IG and 2 on DG). However, I would test this with an extra monitor before spending any money as not all older motherboards support this. If you set the setting to Onboard/Card, then you would only be able to use the two DG ports in this example. Anything hooked up to the IG port would be discarded.
You may ask why you would want to do something like this with Auto. There has been cases where I needed to test the performance of a Website that I was developing on different systems. My main rig has Radeon HD 6970 CF graphic cards so everything on them looks nice. However, I do use the IG graphics to see how a baseline computer's experience on something that could end up being taxing (think scrollable parallax). In some cases, I've even had to go back and optimize some code so that it would appear smoother on IG cards. Much more to this, but it begins to get more outside of the scope of your question.