I/O Hardware

The buses that appear in the figure in the previous slide are:

1. A PCIe (Peripheral Component Interconnect Express) bus, whose purpose is to connect CPUs, cache, and memory to other devices, including disks and I/O devices. The devices connected to this bus are relatively fast.
2. An expansion bus, which connects I/O devices, like the keyboard or mouse. These devices are a bit slower than those connected directly with the PCIe bus.
3. A serial-attached SCSI (Small Computer System Interface) bus, or SAS bus, which moves data from the computer to secondary storage devices.

In that figure, disks are attached either via SAS or via IDE (Integrated Drive Electronics) technologies. SAS is faster than IDE, but IDE is a cheaper tech that supports a greater storage capacity. More on the differences between the two is described in the article at https://getprostorage.com/blog/scsi-vs-sata-vs-ide/.