Plug and Play (PnP)

1. Plug and Play (PnP) By: James Jacobs Jonathan Joyce

2. Plug and Play/Pray? • Purpose: To make computers more user friendly and easier to use • Definition: The technological standard that automatically configures new devices for use • Plug and Pray: There have been problems with PnP

3. Advanced Technology Attachment (ATA) • Proposed by Quantum and Hewlett-Packard • Eliminate use of master/slave jumpers on hard disks • Never became popular • Marketing scheme? • Cable select

4. Peripheral Component Interconnection (PCI) • Developed by Intel, popularized by Microsoft’s Windows 95 and PnP • Before plug and play, several steps either had to be done manually or by a piece of software usually bundled with the new piece of hardware. These tasks include the setting of: interrupted requests (IRQs), direct memory access (DMA), memory addresses, and input/output (I/O). • When a device is configured using plug and play, all of its information is stored in an extended system configuration data file (ESCD).

5. Example of PCI PnP at boot up • Create a resource table of the available IRQs, DMA channels and I/O addresses, excluding any that are reserved for system devices. • Search for and identify PnP and non-PnP devices on the PCI and ISA buses. • Load the last known system configuration from the ESCD area stored in non-volatile memory. • Compare the current configuration to the last known configuration. If they are unchanged, continue with the boot; this part of the boot process ends and the rest of the bootup continues from here.

6. If the configuration is new, begin system reconfiguration. Start with the resource table by eliminating any resources being used by non-PnP devices. • Check the BIOS settings to see if any additional system resources have been reserved for use by non-PnP devices and eliminate any of these from the resource table. • Assign resources to PnP cards from the resources remaining in the resource table, and inform the devices of their new assignments. • Update the ESCD area by saving to it the new system configuration. Most BIOSes will print a message when this happens like "Updating ESCD ... Successful". • Continue with the boot. • (Kozierok 2001)

7. IEEE 1394 • Standard for transmitting real-time data between computers, peripherals, and electronic equipment • High-speed bus (100 to 3200 Mbps) • Uses Open Host Controller Interface for operations • Open HCI can use PCI Bus if necessary

8. Universal Serial Bus (USB) • Extends plug-and-play to a whole new level • Similar to IEEE 1394, but at lower speed (480 Mbps) and more device compatibility • Ability to create device networks • “Hot” plug-and-play device

9. Industry Standard Architecture (ISA) • Older 16 bit architecture • Still used for low-speed devices • Vendors can customize plug-and-play Microsoft Corporation (1994). "Plug and Play ISA Specification." URL: http://www.microsoft.com/whdc/resources/respec/specs/pnpisa.mspx

10. Small Computer System Interface (SCSI) • Uses an adapter from ISA, PCI, or PCMCIA • Contain their own protocols for configuring and managing devices • Ability to create device networks

11. Future of Plug-and-play • Continues to become more user-friendly • Increased device support • Closer to using one device interface (USB for example)