Abstract: A method for providing multiple configurations for a computer system. The method provides interconnection of processor boards in a first configuration and a second configuration. In the first configuration, a first plurality of processor boards are interconnected through a first backplane. In a second configuration, a second plurality of processor boards are interconnected through a second backplane. The first and second pluralities of processor boards are interchangeable with each other.

Abstract: The scalable virtual timer system or subsystem implements multiple hardware timers with minimal silicon overhead. In one embodiment, for each virtual timer of a plurality of virtual timers, a content addressable memory stores a sum of an “initial state” of a free running counter and a desired count duration for the virtual timer. When the stored value matches a current state of the free running counter, the content addressable memory generates a terminal count for the virtual timer. In an alternative embodiment, for each virtual timer, a period register of a set of period registers stores a sum of a desired count duration for a virtual timer and an “initial state” of the free running counter. A comparator of a set of comparators generates a terminal count for a virtual timer when a current state of the free running counter matches the sum stored in a period register associated with the virtual timer.

Abstract: A system provides pseudo-concurrency for a volatile memory and a non-volatile memory on a same data bus. In one system embodiment, the volatile memory is coupled to its own address bus, and the non-volatile memory is coupled to its own address bus. In another system embodiment, the volatile memory and non-volatile memory are coupled to a multiplexed address bus. Concurrent with an access cycle to the volatile memory, the non-volatile memory may be precharged. After the access cycle to the volatile memory, a data cycle to a non-volatile memory may be executed. Concurrent with an access cycle to the non-volatile memory, the volatile memory may be precharged. After the access cycle to the non-volatile memory, a data cycle to the volatile memory may be executed.

Abstract: A microcontroller is presented having a block of logic configurable to perform a selected logic function and to produce output signals coupled to corresponding I/O pads according to a predefined hardware interface. The microcontroller includes a central processing unit (CPU), a first set of I/O pads, and a configurable logic block (CLB) all formed upon a single monolithic semiconductor substrate. The CPU is configured to execute instructions, preferably x86 instructions. The CPU produces CPU output signals during instruction execution. The CLB is coupled between the CPU output signals and the first set of I/O pads, and is configurable to perform a logic function selected from a predefined set of logic functions. Each member of the set of logic functions has an associated hardware interface including a signal table which defines a correspondence between CLB input/output signals and members of the first set of I/O pads.

Abstract: A multiprocessing computer system and method providing multiplexed address and data paths from multiple CPUs to a single storage device. These paths are controlled by an arbitration circuit which allows one CPU to always have the highest priority. The primary CPU may or may not be the highest priority CPU in the arbitration scheme. The arbitration circuit is combined with a controlling mechanism which interfaces to the memory device. This controller operates at a clock rate fast enough to allow the highest priority CPU to access the memory at it's highest data rate and, yet, guarantees a maximum idle period for the lower priority CPU to wait for it's interleaved memory access to complete. A single memory device provides cost and space savings. A controller is responsive to these processors to multiplex their information signals for selectively conveying information present at their address and data ports.

Abstract: An interface between the host CPU and the programmably memory, providing an address, data and read/write control signals to create a non-volatile sector within the programmable memory. In an embodiment when the system reset is de-asserted immediately after power-on, the size of the protected EEPROM area is sensed on special strapping option pins and automatically configures the non-volatile sector. This allows the size of the protected area to be changed on the manufacturing line as needed for different applications. Once configured to protect a specific size and location in the non-volatile memory, the invention prevents the write control signal to the memory to be asserted when the address of the data access requested by the CPU is in the protected area of the memory. This has the effect of preventing modification of the protected area by a sector modification algorithm.

Abstract: A computer system employs a process on warm boot which obviates the need to copy code in non-volatile memory to volatile memory; a normal function in a warm boot process. The computer system checks a warm boot flag which indicates that the code was previously copied on cold boot. By avoiding copying this already copied code and executing directly from the volatile memory considerable time is saved. Since BIOS code is typically on the order of 10K bytes, elimination of the necessity to rewrite BIOS and vectoring directly to BIOS image file in RAM saves on the order of ten thousand clock cycles.

Abstract: In the present invention, a single EEPROM is used to store firmware for the CPU, firmware for the SCP and the system password and other critical system data. Hardware protection is provided that prevents the CPU from accessing the portion of the EEPROM that contains the password or other critical systems data.

Abstract: The invention provides for a CPU in a digital system to control the location of the code being executed by one or more peripheral CPUs when all CPUs share a common memory. This allows the CPU to allocate convenient (e.g., unused) blocks of its address space for the code for the peripheral CPU(s). Additionally, for digital systems in which the peripheral CPU(s) cannot address the full range of the address space of the shared memory that is available to the CPU, the CPU can control the relocation of the block of code for the peripheral CPU(s) (i.e., provide a code paging system).

Abstract: The invention provides a simple I/O port which can be used to support a variety of system functions such as a revision, configuration or identification register. This port is provided with a means to be programmable once, upon system power-up so that changes to the port contents are possible, but only under controlled conditions. Once the register has been programmed, it will no longer respond to writes.

Abstract: An apparatus and method for tracking and interception of instructions as they are presented to the memory, selectively passing harmless data to the device and disallowing the sequences which instruct the device to perform harmful functions, such as self-erase. A software trap is provided to be transparent to the operation of the device and the host system, imposing no harmful timing delays or software overhead. Accordingly, the invention allows the use of standard electrically erasable read-only memories in an application which requires that the device be protected from global erasure. A hardware front end intercepts the software command which is used to globally erase the device.

Abstract: A plurality of processors form a network used to communicate with one or more peripheral devices and the system control processor. One processor is dedicated to at least one peripheral device. Since the system control processor is not burdened with the relatively slow communications protocol with the peripheral devices, it is free to do other tasks which improves the overall system performance. Communication protocol between the dedicated processors allows for local and global communication.

Abstract: A personal portable computer having a fluorescent backlit LCD is provided with circuitry for mitigating noticeable flicker of the backlight. The signal driving the backlight is synchronized with the display refresh signal. More particularly, a horizontal sync signal from an LCD driver is applied to a counter which divides the horizontal sync signal by a predetermined amount. The counter is reset after each frame of the display is written by a vertical sync signal. The output of the counter is applied to a pluse width modulator, such as a monostable multivibrator, which provides a signal to the backlight, synchronized with the display refresh signal. The circuitry also allows for the duty cycle of the backlight signal to be adjusted to control the brightness of the display and consequently the power drain on the battery.