The Extended System Configuration Data (ESCD) is a specification for configuring

x86 x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was introd ...

computers of the

ISA PNP The term Legacy Plug and Play, also shortened to Legacy PnP, describes a series of specifications and Microsoft Windows features geared towards operating system configuration of devices, and some device IDs are assigned by UEFI Forum. The stan ...

era. The specification was developed by

Compaq Compaq Computer Corporation (sometimes abbreviated to CQ prior to a 2007 rebranding) was an American information technology company founded in 1982 that developed, sold, and supported computers and related products and services. Compaq produced ...

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...

and Phoenix Technologies. It consists of a method for storing configuration information in nonvolatile BIOS memory and three

BIOS In computing, BIOS (, ; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the ...

functions for working with that data. The ESCD data may at one time have been stored in the latter portion of the 128 byte extended bank of battery-backed CMOS RAM but eventually it became too large and so was moved to BIOS flash. It contains information about

ISA Isa or ISA may refer to: Places * Isa, Amur Oblast, Russia * Isa, Kagoshima, Japan * Isa, Nigeria * Isa District, Kagoshima, former district in Japan * Isa Town, middle class town located in Bahrain * Mount Isa, Queensland, Australia * Mount Is ...

PnP devices is stored. It is used by the

to allocate resources for devices like expansion cards. The ESCD data is stored using the data serialization format used for EISA. Its data starts with the "ACFG" signature in ASCII. PCI configuration can also be stored in ESCD, using virtual slots.ESCD specification 1.02A
Appendix A, pp. 21-22 Typical storage usage for ESCD data is 2–4 KB The BIOS also updates the ESCD each time the hardware configuration changes, after deciding how to re-allocate resources like IRQ and

memory map In computer science, a memory map is a structure of data (which usually resides in memory itself) that indicates how memory is laid out. The term "memory map" can have different meanings in different contexts. *It is the fastest and most flexible ...

ping ranges. After the ESCD has been updated, the decision need not be made again, which thereafter results in faster startup without conflicts until the next hardware configuration change.

References

External links

ESCD Support for 2.4.6-ac1/PNPBIOS (was: reading/writing CMOS beyond 256 bytes?)
Motherboard BIOS {{compu-hardware-stub

References

Further reading

External links