System buses (lecture 5)

PCI Express system bus is a set of independent serial bi-directional data transmission channels combined in a star topology.

Each of the devices participating in the exchange is connected to the opposite end of the channel. Thus, a point-to-point connection is established between each device and the switch. Thanks to this scheme, any device through a switch can be connected to any other, which is required from the system bus.

Can the PCIe connection be said to meet the system bus requirements?

How is information transmitted in PCIe?

Information in PCI Express is transmitted in packets, which can contain data, addresses, service requests, etc., and all types of packets are transmitted over the same lines as data packets. Information exchange is carried out simultaneously (but not synchronously) on all available lines.

Host Bridge.

of devices that implement PCIe:

Switch: The switch manages multiple PCIe streams.

PCIe endpoint: An I/O device or controller that implements PCIe, such as a Gigabit Ethernet switch, a graphics or video controller, disk interface, or a communications controller.

Legacy endpoint: Legacy endpoint category is intended for existing designs that have been migrated to PCI Express, and it allows legacy behaviors such as use of I/O space and locked transactions. PCI Express endpoints are not permitted to require the use of I/O space at runtime and must not use locked transactions. By distinguishing these categories, it is possible for a system designer to restrict or eliminate legacy behaviors that have negative impacts on system performance and robustness.

PCIe/PCI bridge: Allows older PCI devices to be connected to PCIe-based systems.

What kind of devices that implement PCIe may attach to PCIe links from the chipset?

well as circuitry and logic to support ancillary features required in the transmission and receipt of the 1s and 0s.

Data link: Is responsible for reliable transmission and flow control. Data packets generated and consumed by the DLL are called Data Link Layer Packets (DLLPs).

Transaction: Generates and consumes data packets used to implement load/ store data transfer mechanisms and also manages the flow control of those packets between the two components on a link. Data packets generated and consumed by the TL are called Transaction Layer Packets (TLPs).

Above the TL are software layers that generate read and write requests that are transported by the transaction layer to the I/O devices using a packet-based transaction protocol.