Question #3
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Can you draw a system hardware diagram and label the places where the following types of addresses will be seen in the physical hardware? Virtual, logical, physical, and I/O?
Answer
A typical system diagram of the hardware will draw the processor in the upper left-hand corner, often with RAM and FLASH devices to its immediate right, all of which connect to the processor bus drawn immediately below these devices.
A bridge device is then drawn below, and connected to, the processor bus. Below the bridge is an I/O bus, often PCI, to which the various I/O devices of the system are connected.
Virtual and logical addresses are used only in the internals of the processor by the program being executed: probes into the silicon would be needed to see them in the hardware.
Physical addresses are used on the processor bus, outside the processor on its addressing pins: Programs make use of physical addresses but only indirectly, by programming them into devices such as the processor's Memory Management Unit and the North Bridge device.
Understanding where and when these different forms of addressing may be used is a core issue in embedded Linux development. RyteTyme can show your engineers how to avoid these pitfalls.
