When connection between a computer body and an expansion unit has been detected, a system BIOS detects whether or not a storage device in an access lock state exists in the expansion unit. If a storage device in the access lock state exists, the system BIOS issues APM event to turn on a high-order driver...http://www.google.com/patents/US5911042?utm_source=gb-gplus-sharePatent US5911042 - Computer system having expansion unit
