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Extended system configuration data (ESCD) is a portion of the nonvolatile basic input/output system (BIOS) memory (also known as complementary metal-oxide-semiconductor (CMOS) memory) on a personal computer motherboard. This is also where the ISA PnP device data is located. ESCD is employed by the BIOS to assign resources for hardware extensions, commonly called expansion cards.
With each ESCD hardware configuration change, a corresponding BIOS memory change is established after the processor determines how to locate sufficient resources i.e. interrupt request line (IRQ) and memory mapping ranges. Once the ESCD is updated, there is no need to repeat this decision process until the user decides to make the next hardware configuration change. This automation creates prompt and efficient results obtained from a faster startup without any conflicts.
An ISA configuration utility (ICU) is also dedicated to update the ESCD through PnP BIOS interfaces. The Microsoft Windows operating system device manager allows a user to view the ICU configuration and make the needed or desired changes. For example, any PC motherboard hardware expansion card may be disabled from the device manager.