Hardware Detection Phase

During the hardware detection phase, Windows 95 Setup analyzes installed computer components, and detects installed hardware devices and connected peripherals. Windows 95 Setup also identifies the hardware resources that are available (for example, IRQs, I/O addresses, and DMAs), identifies the configuration of installed hardware components (for example, IRQs in use), and builds the hardware tree in the Registry.

Windows 95 Setup uses several mechanisms to detect installed hardware devices:

• For a non-Plug and Play-compliant computer (called a legacy computer), Windows 95 checks for known hardware devices by checking I/O ports and specific memory addresses to attempt to identify whether they are being used by known devices. Windows 95 also checks for Plug and Play peripherals connected to legacy computers, which return their own device identification codes.
• For a computer with a Plug and Play BIOS, Windows 95 queries the computer for installed components and their configuration. Windows 95 also checks the computer for connected Plug and Play peripheral devices.

During this phase, Windows 95 Setup tries to identify and resolve hardware conflicts.

Setup uses the Windows 95 hardware detection module to detect hardware components. If a Plug and Play device is detected, its configuration information is added to the Registry. Device drivers are installed based on the Registry settings. Plug and Play ensures that the correct files are installed and that the configuration options are set properly each time Windows 95 is started. For information about Plug and Play, see Chapter 18, "Introduction to System Configuration" and Chapter 31, "Windows 95 Architecture."

Windows 95 uses the same hardware detection procedures when you run the Add New Hardware option in Control Panel, when you use the PCMCIA wizard to enable protected-mode support, and the first time you start a computer using a new docking state.

For more information about how detection works, see "Safe Detection, Safe Recovery, and Verification" later in this chapter.