It depends on the specific motherboard design, I give an example, strix b250F,
Let's first look at the b250 native specifications, mainly look at the sata port and integrated network card information, intel's official database shows that b250 native 6 sata3, integrated a network card.
Look at the design of the b250f, two m2, each 4 pcie 3.0, sata port 6, one network port, which indicates that there is no additional chip to expand the interface, that is, there are still 4 pcie, let's look at the motherboard, there are just 4 pcie x1, which is exactly 12.
The reason for these two steps, I will also say,
Some motherboards will add asmedia's sata chip to expand the sata port, x370, z270 and so on are native to 6, if more than 6 is definitely added chip expansion;
Dual network card motherboard must use the chip to expand, a network card generally occupies one;
The pcie x1 interface of the mainboard is definitely provided by the mainboard chipset, and the pcie of the cpu is only 16, 8, and 4.