What a PCI Base Address Register Is
A PCI Base Address Register tells the computer where a card's control panel lives in memory. The card says at start-up how big a region of addresses it needs, the system picks a free place for it and writes the chosen address back into that register, and your driver reads it to learn which addresses to poke to make the card do things. Guess the address instead and you write into something else's memory.
Questions this Concept answers
- Why is the address in a base address register written there by the system rather than fixed by the card's maker?
Base Address Register Types, Sizing, and Address Assignment in PCIe
A Base Address Register (BAR) is a field in a PCIe device's configuration space that maps the device's memory or I/O resources into the system's address space, allowing the root complex/CPU to access…