I/O addresses

Input/Output (I/O) addresses represent special locations in system memory that are reserved for a particular device. As information is passed back and forth between the peripheral device and the CPU, the I/O address is a common place for this information to reside. I/O address ranges can vary in size, depending on the type of device. As with IRQs, I/O addresses must be unique for each device. Table 19-2 is a list of the most frequently used I/O addresses and the devices that use them.

Table 19-2

Summary of Common I/O Addresses and Devices

Direct memory access

Direct Memory Access (DMA) channels are used to facilitate the transfer of data from a peripheral device directly to system memory. Information transfer is faster and more efficient because it doesn’t have to go through the CPU to get to system memory. DMA channels are used most often by sound cards, but they are a scarce resource — only seven of them exist.

Laptop Considerations

7.13 Identify and maintain mobile system hardware (e.g., PCMCIA, APM)