Must a CPU have a GPU if the motherboard provides a display port (when there isn't any separate video card)?

Today, motherboard-integrated graphics are basically gone (in the consumer sector, anyway). It’s either CPU-integrated graphics or dedicated graphics. Both Intel and AMD still sell CPUs without integrated graphics, even with the same socket. If you install one of these, you won’t be able to use the display connectors on the motherboard.

In the past, CPUs did not have integrated graphics at all. Instead, the graphics unit was integrated with the motherboard (typically directly with the chipset). Your older Phenom II configuration comes from this time. It has motherboard-integrated graphics.

If you want your monitor to work there has to be a graphics controller in the system somewhere. That graphics controller needs fast reliable access to a section of RAM to use as a frame buffer. Even if you don't want your monitor to work you may well find your motherboard won't boot without a graphics controller. A graphics controller is a pretty key part of the traditional PC hardware though I see reports that the dependency may have weakened in recent years.

Depending on the system, the graphics controller may be in a few different places.

  • A separate device with its own dedicated ram.
  • Integrated as part of the CPU
  • Integrated as part of the chipset
  • Integrated as part of the management controller (note that such graphics controllers are intended to provide a graphics output for installation and initial setup, their performance/features are terrible by modern standards).

On AMD AM2/2+/3/3+ and Intel LGA775, the onboard graphics were normally provided by the northbridge. So they would work with any CPU the motherboard works with.

On Intel LGA1366 and LGA2xxx, there is no provision for integrated graphics in either the CPU or the chipset. Most boards with these sockets will not have onboard graphics at all. The main exception being server boards that have the graphics controller integrated with the management chipset.

On Intel LGA115x and AMD AM4, the graphics controller is integrated with the CPU and not all CPU models offer it. So generally on boards with these sockets, if you want to use the onboard graphics you have to use a CPU that provides a graphics controller. The exception again being some server boards that have a graphics controller as part of the management chipset.