A place in the computer's PnP BIOSs where information about peripheral devices is stored that reflects the status of the systems configuration the last time the computer was booted. This applies mainly to early motherboards, more commonly referred to as "legacy" equipment. Some motherboards have a BIOS which allows you to delete the ESCD information from the BIOS after an older legacy card has been removed from the motherboard.
You will also find additional information regarding ESCD at this Phoenix/Award Link.
Some BIOSs have a setting in the PnP section called "Reset Configuration Data". If you receive a message "updating ESCD...." you can the also manually "reset" the configuration of the computer's ESCD.
On some motherboards operating with EDO memory you can also try Enabling the EDO DRAM install option which is found in the Chipset Features section of the BIOS. As a last alternative try disabling the external cache which is also located in the BIOS. For M-technology motherboards you might have to set the bios jumpers to program mode (or 5V Flash mode).ESCD (Extended System Configuration Data)
At times the Extended System Configuration Data update will fail in the BIOS as the system boots. The problem occurs with AMI and Award BIOS versions that used a poor method to prevent using compressed BIOS code while updating ESCD (Extended System Configuration Data) memory area in the BIOS. This has, for the most part, been eliminated in the PnP Bios releases.
Most generally, those computers equipped with the OverDrive® processor diagnostics will verify this before the installation of the OverDrive processor as it checks to see if the ESCD addresses are being aliased to the 4 GB memory range.
All Intel OPSD BIOS's do not alias ESCD memory area, but use an Intel patented method to prevent the problem.