What is a pci bridge
![what is a pci bridge what is a pci bridge](https://sipilpedia.com/wp-content/uploads/2021/03/34-681x887.png)
It is a bridge (conceptually a Host-to-PCI bridge) that lets the CPU performs PCI transactions.įor example, in the x86 case, any memory write or IO write not reclaimed by other agents (e.g. The CPU doesn't generate PCI transactions natively, a Host Bridge is necessary. They are logical, however, it is advised to number the busses sequentially from the root.
#What is a pci bridge software#
It's important to note that these ID addresses are assigned by the software (but for the device part, which is fixed by the wiring). In order to access the CAS of a device, the devices must be addressable.Įlectrically, each PCI slot (either integrated or not), in a PCI bus segment, is wired to create an addressing scheme made of three parts: device (0-31), function (0-7), register (0-255).Įach device can have up to seven logical functions, each one with a CAS of 256 bytes.Ī bus number is added to the triple above to uniquely identify a device within the whole bus topology (and not only within the bus segment). The third one is used to access the configuration address space (CAS) of each device within this CAS it's possible to meta-configure the device.įor example, where it is mapped in the system memory address space. The first two are assumed to be required knowledge. PCI defined three types of transactions: Memory, IO and configuration. In the picture above, two segments are shown (PCI BUS 0 and PCI BUS 1). Informally, each PCI bus is called a PCI segment. The secondary bus can be another PCI bus (the device is called a PCI-to-PCI bridge, henceforward P2P) or a bus of a different type (e.g. To create more complex hierarchies some devices can operate as bridge: a bridge connects a PCI bus to another, secondary, bus.
![what is a pci bridge what is a pci bridge](https://tldp.org/LDP/tlk/dd/pci-system.gif)
The Conventional PCI bus (henceforward PCI) is a designed around the bus topology: a shared bus is used to connect all the devices.
![what is a pci bridge what is a pci bridge](http://www.eurekatech.com/images/products/pci/ep440.gif)
Skip to the last section to read the answers. I'll try to fix my terminology with a brief and incomplete summary of the PCI and PCI Express technology.