1. Plug-and-Play

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. “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

9. “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

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