Plug and Play Plug and play

in 1995, microsoft released windows 95, tried automate device detection , configuration as possible, still fall manual settings if necessary. during initial install process of windows 95, attempt automatically detect devices installed in system. since full auto-detection of new process without full industry support, detection process wrote progress tracking log file during detection process. in event device probing fail , system freeze, end-user reboot computer, restart detection process, , installer use tracking log skip past point caused previous freeze.

at time, there mix of devices in system, capable of automatic configuration, , still using manual settings using jumpers , dip switches. old world of dos still lurked underneath windows 95, , systems configured load devices 3 different ways:

through windows 95 device manager drivers only
using dos drivers loaded in config.sys , autoexec.bat configuration files
using both dos drivers , windows 95 device manager drivers together

microsoft not assert full control on device settings, configuration files include mix of driver entries inserted windows 95 automatic configuration process, , include driver entries inserted or modified manually computer users themselves. windows 95 device manager offer users choice of several semi-automatic configurations try free resources devices still needed manual configuration.

an example of isa interface card extremely limited interrupt selection options, common problem on pc isa interfaces.

kouwell kw-524j dual serial, dual parallel port, 8-bit isa, manufactured in 1992:

* serial 1: irq 3/4/9

* serial 2: irq 3/4/9

* parallel 1: irq 5/7

* parallel 2: irq 5/7

(there no technical limitation 3,4,5,7,9 not selectable choices each port.)

also, although later isa devices capable of automatic configuration, common pc isa expansion cards limit small number of choices interrupt request lines. example, network interface might limit interrupts 3, 7, , 10, while sound card might limit interrupts 5, 7, , 12. results in few configuration choices if of interrupts used other device.

the hardware of pc computers additionally limited device expansion options because interrupts not shared, , multifunction expansion cards use multiple interrupts different card functions, such dual serial port card requiring separate interrupt each serial port.

because of complex operating environment, autodetection process produced incorrect results, in systems large numbers of expansion devices. led device conflicts within windows 95, resulting in devices supposed self-configuring failing work. unreliability of device installation process led plug , play being referred plug , pray.

up until 2000, pc computers still purchased mix of isa , pci slots, still possible manual isa device configuration might necessary. successive releases of new operating systems windows 2000 , windows xp, microsoft had sufficient clout drivers not provided older devices did not support auto-detection. in cases, user forced purchase new expansion devices or whole new system support next operating system release.