Abstract: A computer system has a ROM device containing two separately flashed areas. Each area contains a firmware image. From the factory, the two firmware images are identical. Each image also contains the executable code to flash an image area. The ROM also contains a “boot block” sector that makes decisions as to which of the firmware images is the “active” image and which is the “inactive” image. The active image is copied from the ROM to a RAM device and executed from RAM during normal system operation. The inactive image normally is not executed. The boot block sector also contains code that performs a checksum verification on the active image during initialization and, if the checksum fails, switches the active/inactive status of the two firmware images to make the previously inactive image the active image. With two firmware images, the system can recover from a power failure occurring while flashing the ROM because the other firmware image is still available.

Abstract: An apparatus supports both (1) a cost-effective graphics device (such as an AGP device) integrated onto the motherboard, and (2) an upgradable computer system with an add-in card slot for receiving a second graphics device (such as a second AGP device) on a card. The apparatus is connected to a bus that has a first set of signals which is sensitive to noise. The apparatus also has a first switch connected to a first device, the first switch being connected to the first set of signals on the bus. The apparatus has a second switch which is adapted to be connected to a second device. The second switch is also connected to the first set of signals on the bus. The apparatus also has a detector connected to the first and second switches to enable the first switch if the first device is selected and otherwise enable the second switch.

Abstract: A method that identifies the type of LCD panel used in a portable computer system based on the frequency of the oscillator signal of the DC-to-AC inverter in the LCD panel. In this method, only one signal is routed from the LCD panel to the base unit of the portable computer system for the purpose of panel identification. The inverter oscillating signal is used to increment a counter during power on operations. A system counter, which is clocked by a system clock, is used to determine the number of system clocks needed for the panel identification counter to reach a predetermined count. That number is compared with the entries of a table, in which each entry corresponds to a type of LCD panel. In this manner, the type of LCD panel can be identified based on the frequency of the inverter signal. A corresponding entry in a second table is accessed to obtain a table entry for the identified LCD panel to a full table of LCD panel parameters. The table entry is stored in a predetermined location in the Video ROM.

Abstract: In a data bus with m data bits, electromagnetic interference is produced by polarity switching the data on that data bus. When two consecutive data items result in a change of over half of the data bits, the polarity of the second data item is switched, and a polarity signal is correspondingly switched on the data bus. When the data is received, it is restored to its original polarity by adjusting the polarity of the received data according to the signal on the polarity line. In this way, the total number of bit transitions between any two data items is reduced to a maximum of m/2.

Abstract: A method that identifies the type of LCD panel used in a portable computer system based on the frequency of the oscillator signal of the DC-to-AC inverter in the LCD panel. In this method, only one signal is routed from the LCD panel to the base unit of the portable computer system for the purpose of panel identification. The inverter oscillating signal is used to increment a counter during power on operations. A system counter, which is clocked by a system clock, is used to determine the number of system clocks needed for the panel identification counter to reach a predetermined count. That number is compared with the entries of a table, in which each entry corresponds to a type of LCD panel. In this manner, the type of LCD panel can be identified based on the frequency of the inverter signal. A corresponding entry in a second table is accessed to obtain a table entry for the identified LCD panel to a full table of LCD panel parameters. The table entry is stored in a predetermined location in the Video ROM.

Abstract: A low quiescent current voltage regulator particularly suited for providing current to the RTC/CMOS memory section of a notebook computer. The gate of the JFET is grounded, the drain connected to the main battery and the source connected to the RTC voltage input of the RTC/CMOS memory section. The JFET source voltage approaches the gate-source cutoff voltage of the JFET. This cutoff voltage is selected to be in the proper range for the RTC/CMOS memory section. A complete RTC voltage control circuit is configured to provide 5 volts from the system voltage when the computer is turned on, 3 to 5 volts from the JFET when the computer is turned off and the main battery is present and 3 volts from the RTC battery when the computer is turned off and the main battery is removed.

Abstract: An LCD precharge regulator circuit providing current directly from the input battery voltage to precharge the LCD display. A first switch activates a precharge regulator coupled to the unregulated DC input voltage, to supply the power for the initial current surge from the DC input to charge the LCD display. The precharge regulator includes a transistor and a biasing circuit. The biasing circuit initially turns the transistor fully on, but increasingly biases the transistor off as the LCD display charges to just below the operating voltage of the LCD display. A delay circuit activates a second switch after the LCD display is substantially charged, where the second switch connects the supply voltage from the DC/DC converter to the LCD display. At that point, the transistor is biased off, isolating the LCD display from the DC input voltage. Thus, the supply voltage need only sustain the charge on the LCD display after being substantially charged.