ISA Devices

Industry Standard Architecture (ISA) bus design is the architecture specified for the IBM® PC/AT®. Plug and Play ISA devices can be used on existing computers, because the specification does not require any change to ISA buses. For automatic configuration of Plug and Play ISA devices, the system performs the following actions:

• Identifies and configures the devices using I/O ports, which enables the Plug and Play logic on the card.
• Isolates each card and assigns a unique device ID and serial number.
• Reads the resource requirements and capabilities stored on each card.
• Allocates resources to each card, which reserves these resources so that other Plug and Play cards in the computer cannot be assigned these resources.
• Activates the Plug and Play ISA cards.

For legacy devices, standard ISA cards can coexist with Plug and Play ISA cards on the same computer. Windows 95 determines the type of hardware and its configuration during Setup, either by polling the hardware or asking the user to supply values. This configuration information is stored as static values in the Registry, and cannot be changed dynamically, but it is used to determine resource assignments for Plug and Play-compliant devices.