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I am learning about the PCI bus, and there is something that I am not sure of. A motherboard have some PCI slots to put the PCI cards in:

enter image description here

Now when we say that we have a PCI bus, do we mean that the PCI bus only consists of the devices in the PCI slots, or are there other devices that are not in the PCI slots that are also considered to be a part of the PCI bus?

For example, the following is a VGA card that is built-in into the motherboard (it is not a separate PCI VGA card):

enter image description here

Does this built-in VGA card also considered to be a part of the PCI bus?

closed as off-topic by gnat, amon, 8bittree, Bart van Ingen Schenau, Thomas Owens Oct 12 '17 at 22:36

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    I'm voting to close this question as off topic because it is not about the software development life-cycle, such as software design or architecture. Please see our help center for details. Specifically, your question seems to be about hardware concepts, not software engineering concepts. – amon Oct 8 '17 at 19:46
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Now when we say that we have a PCI bus, do we mean that the PCI bus only consists of the devices in the PCI slots, or are there other devices that are not in the PCI slots that are also considered to be a part of the PCI bus?

Yes, a device does not have to be on a PCI card in a PCI slot to be connected to a PCI bus. It could be connected to the bus in some other fashion. For example, if you remove the slot from the motherboard, and then solder the connections directly to the pins of the PCI card, the device would still be connected to the PCI bus, but it would not be in a PCI slot.

On many older motherboards, the USB Host Controller and ATA Host Controller are connected to the PCI bus, but soldered onto the motherboard directly, not sitting on a PCI card in a PCI slot.

For example, the following is a VGA card that is built-in into the motherboard (it is not a separate PCI VGA card)

That is not a VGA card, that's a VGA connector. It is very likely that the VGA chip is not connected to the PCI bus but rather via a specialized interface to the Northbridge. (Or, it may even be part of the Northbridge and not a separate chip at all.)

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Computers come with built-in input & output ports e.g USB ports, Ethernet adapter and VGA card. And manufactures think that people will need other input output devices then they made PCIs to plug in those other devices.

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    Please don't answer off-topic questions, but flag them for closure instead. – Glorfindel Oct 10 '17 at 11:04

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