Plug-and-Play

Introduction Automatically detects new hardware devices and assigns resources Compaq, Intel, Phoenix Requires PnP-compatible BIOS, OS, and devices PCI designed with PnP in mind; ISA was not Microsoft (later) – Universal PnP – based on PnP but for networks

How It Works Non-PnP devices: “legacy devices” First scans for legacy devices Then scans for PnP devices Checks against ESCD (extended system configuration data) If change found, new configuration saved, and resources allocated (first to legacy devices, then to PnP devices) If OS is PnP-compatible, it takes over configuration; otherwise BIOS does

How It Works PCI Local Bus 64 bytes of configuration registers Vendor ID, Device ID, Base Address Register (BAR), Interrupt Line Register Vendor ID & Device ID: identify manufacturer and specific PnP device BAR tells which resources needed First bit – I/O or memory space Rest – how much space is needed

How It Works Interrupt Line Register – which hardware interrupt needed Other registers – not specifically for PnP BIOS checks PCI slots for device present Hexadecimal FFFF – no device detected

How It Works OS registry – devices, their drivers, resources they use Application software – info from registry rather than registers Windows device manager – view configuration settings Windows NT – not truly PnP, but software setup programs will make changes to registry Windows NT diagnostics – view configuration settings

Benefits Ease of installation of new hardware components No switches and jumpers needed Backward compatibility with legacy devices Configuration utility Easier for inexperienced computer users

“Plug-and-Pray” Does not always work correctly Worse when there is a mixture of legacy devices and PnP devices on system Functions best when all devices are PnP-compatible BIOS and devices must be PnP-compatible Not all PCI devices PnP

“Plug-and-Pray” As technology improves, problems decrease ISA will be used less and PCI more Less combinations of legacy devices and PnP devices Improvements on PnP BIOS

Conclusion Computers more usable Long term goals – UPnP Interconnectivity in household, all based on concept of PnP