Abstract: A system comprises a first graphics controller adapted to couple to a first display, a second graphics controller adapted to couple to a second display, and a switch through which at least one of communications and power is provided to the second graphics controller. The system also comprises control logic coupled to the switch. The control logic causes the switch to preclude at least one of communications and power from being provided to the second graphics controller if the second display is not operatively coupled to the system.

Abstract: A laptop computer system executes automatic battery calibration to improve the accuracy of the battery's internal charge monitor. The calibration procedure drains the battery to approximately 0% of charge capacity during normal computer operation, permitting a user to operate the computer without risking power failure when the battery discharges. The computer returns to normal operation if either the AC power or the battery is removed. During the calibration procedure, the computer system prevents power management software from forcing shut down before the battery completely drains.

Abstract: A method and apparatus for sensing the state of a computer system and changing the state, if necessary, before connecting the computer system to a computer expansion unit. The computer system has an electrical sense pad on which it sets a state signal. This state signal can indicate one of several states of the computer system. When the computer system is placed in the computer expansion unit, the expansion unit detects the state signal from the electrical sense pad and determines the state of the computer therefrom. If the determined state is an acceptable state, then the expansion unit will complete the connection of the computer to itself. If the determined state is an unacceptable state, then the expansion unit will delay completion of the connection and will send a signal back to the computer system telling the computer system to change its state.

Abstract: A shared keyboard and system ROM uses a single ROM for both the keyboard and the system operating system information (BIOS). The shared ROM is never simultaneously used for both of these functions. At initial boot-up, the system processor executes from the shared ROM to copy the system BIOS information to the system Random Access Memory DRAM. Once this copying has been completed, the shared ROM then is used by the keyboard subsystem. Different address ranges are employed in the shared ROM for the keyboard information and for the system BIOS.

Abstract: A circuit for connecting the power supply output of a computer to ground when the system is shut down to counter adverse effects of backfeed voltage which includes a MOSFET between the power supply output and ground. In one embodiment the MOSFET is switched on by a signal that deactivates the system power supply. In an alternative embodiment, two MOSFETs are used. The first MOSFET is controlled directly by the power supply output and shorts the second MOSFET's gate to ground when the power supply output generates a significant voltage. If the second MOSFET's gate is grounded, the MOSFET deactivates and opens a circuit between the power supply output and ground. When the power supply is turned off, the second MOSFET activates and grounds the power supply output. A resistor between the power supply output and ground allows the power supply to generate five volts when the system is power cycled and deactivate the second MOSFET.