Page 36 - UNI 101 Computer Science Handout.

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Figure 9 A Personal Computer Motherboard

For example, numerous manufacturers produce various I/O modules mounted on printed circuit cards

that plug into the PCI-Express bus that is provide don the backplane of nearly every current ‘‘PC-
compatible’’ model. (PCI bus interface capability is also available on most midsize and mainframe

computers, including recent IBM mainframes.) Most PC models also support plug-in cards for older PCI

slots. Bus interface switching circuitry in the PC connects memory and the PCI-Express bus together

during DMA transfers, which provides the required CPU-memory-I/O link. PCI and PCI-Express cards

provide graphic display support, audio capability, serial and parallel ports, modem connections, Ethernet
interfaces, and many other functions, demonstrating the advantages of standardization.

Although Intel originally designed the PCI backplane, it and its PCI-Express success or have become

standards through common use and agreement. The ability to interconnect buses also provides flexibility

for the future; as bus designs evolve, new bus interfaces can be implemented to add the capabilities of
new and improved buses to the system. Figure below shown an interconnection of two buses also

suggests that memory and I/O devices will often be connected to different buses. The bus interface

36 Academic Year 2025/2026