8.1 Overview

The Input/Output (I/O) subsystem exists on most operating systems for three main reasons:

Usually, the I/O software is structured in layers:

The interrupt handler is mainly responsible for starting up a device driver after an I/O operation completes. The device driver performs device-specific operations, such as setting up registers for DMA and checking device status. The device-independent system interface provides a uniform interface to user-level software and common I/O functions (that is, protection, blocking, buffering) that can be performed across different devices.

For the RCP, there are two modes of I/O operations:

The RCP consists of the following major devices and interfaces (see Figure 8-1 below):

Reality Signal Processor(RSP)
This internal processor supports both DMA and I/O operations between RDRAM and I/Dmem addresses.
Reality Display Processor(RDP)
This internal processor supports only DMA from either RDRAM or Dmem addresses to its internal buffer.
Video Interface(VI)
This write-only interface connects to the video DAC. It supports only DMA from RDRAM to a specific video buffer address and allows you to change video modes and configurations.
Audio Interface(AI)
This write-only interface connects to the audio DAC. It supports only DMA from RDRAM to a specific audio buffer address and allows you to set the audio frequency.
Parallel Interface(PI)
This read-write interface connects to the ROM cartridge and other mass storage devices. It supports DMA as well as I/O Read/Write to ROM addresses.
Serial Interface(SI)
This read-write module interfaces to the PIF, which connects to the game controller and modem devices. It supports DMA as well as I/O Read/Write to PIF RAM addresses.
Figure 8-1 Logical View of RCP Internal Major Devices and Interface Modules
[Figure 8-1]

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