Abstract: A computer system provides a program access to a first register during real mode operation by using an index register and a data register, wherein the index register and the data register are located in real mode memory space and the first register is located outside of real mode memory space.

Abstract: An address translation apparatus and method that can convert a limited-range memory address from a peripheral device to an expanded-range memory address on the fly. The invention can expand the limited address capability of a peripheral bus, such as a PCI bus with a 4 GB address range, to a much larger address capability, such as a 64 GB address range. This conversion can be performed on the fly by hardware, so that no appreciable delay in transfer time is created. The conversion can be performed by adding features to a conventional graphics controller interface, thus minimizing the impact on circuit complexity and system cost.

Abstract: An approach to selecting either an actual stepping revision ID value or a compatible revision ID value to be readable by a processor through a revision ID register.

Abstract: A method and apparatus for delivering APIC interrupts to a processor, and between processors, as FSB transactions. Interrupts and hardware signals, generated by a PCI device, are converted into an upstream memory write interrupt and further converted into an FSB interrupt transaction, received by a processor. Interrupts marked as lowest priority re-directable are redirected based on task priority information. Support for XTPR transactions to update XTPR registers is provided. Preferred ordering of XTPR update transactions and interrupts to be redirected is provided.

Abstract: An approach to selecting either an actual stepping revision ID value or a compatible revision ID value to be readable by a processor through a revision ID register.

Abstract: A computer system comprises a direct memory access (DMA) transfer unit and a plurality of DMA devices coupled by an external bus. The DMA transfer unit effectuates DMA transfers for the plurality of DMA devices. The DMA transfer unit contains a DMA controller, a bus arbiter, and a bus controller. The DMA controller and the bus controller generate a two-clock cycle DMA transfer. To effectuate a two-clock cycle DMA transfer, a requesting DMA device sets-up a DMA transfer with the DMA controller such that a DACK# signal is asserted during a first clock period. During a second clock period, the DMA controller sets-up the memory address. During a third clock period, the bus controller transitions a command signal on the external bus. Upon assertion of the command signal, valid data is asserted on the external bus. For demand and block mode operations, additional DMA transfers are executed in a two-clock cycle DMA transfer. The DMA controller and the bus controller also generate a three-clock cycle DMA transfer.

Abstract: A method and apparatus for regulating the deferral of a transaction issued on a bus by a processor in a computer system is disclosed. A bus transaction recorder coupled to the bus processes encoded signals from the transaction issued on the bus. A line coupled to the bus sends an indication signal when a pending transaction request is issued on the bus. A CPU latency timer times the current transaction on the bus when a new pending transaction is waiting on the bus. The CPU latency timer outputs an expiration signal when the transaction takes more than a predetermined amount of time to complete. A transaction processor unit is coupled to the bus transaction recorder, the line, and the CPU latency timer.

Abstract: Apparatus and a method for eliminating deadlock in a multibus computer system which system includes a primary bus, and a secondary bus, a bridge circuit for joining the primary bus to a bus master, and a second bridge circuit for joining the primary bus to the secondary bus. The invention causes the second bridge circuit to generate a first signal directed to the all bridge circuits to indicate that a bus master on the secondary bus desires access to the secondary bus. All bridge circuits holding data directed to a component on the secondary bus flushes all temporary storage means holding data directed to a component on the secondary bus. The bridge circuits then generate signals to indicate that flushing is complete and the bus master on the secondary bus is granted access to the secondary bus.

Abstract: A buffer circuit for transferring data between a first slower narrower computer bus and a second wider faster computer bus which buffer circuit includes first and second buffers each capable of storing a plurality of bytes of data equivalent to the width of the second bus, a single address register for holding an address which represents data in either of the two buffers, the lowest order bit of the address register indicating to which one of the two buffers data is being written, first and second registers for storing indications of valid data in the first and second buffers, and a control circuit for controlling the filling of the first and the second buffers in accordance with the byte addresses furnished and the flushing of the first and the second buffers whenever a most significant byte of a buffer has valid data, whenever an attempt is made to write to a buffer address containing valid data, and whenever an attempt is made to load data to a buffer address different than an address in the address regist

Abstract: A computer system having a responsive low-power mode and a full-power mode of operation. The computer system includes a power consumption controller, a processor and a communication device. The power consumption controller generates an interrupt signal in response to a low power event or a fully operational event. The power consumption controller also generates a clock control signal. The clock control signal is deasserted during the full-power mode of operation and alternatively asserted for a first duration and deasserted for a second duration during the low-power mode of operation. In response to an asserted clock control signal, the processor suppresses the internal clock signal to at least one functional block within the processor and in response to a deasserted clock control signal, the processor transmits the internal clock signal to at least one functional block within the processor.

Abstract: A circuit for controlling interrupt request signal transmission in a computer system. An input receives an interrupt request from an external component. First circuitry coupled to the input generates a signal in response to the interrupt request from the external component. The signal causes a processor to switch to fully operational mode. Second circuitry coupled to the input generates an interrupt request signal to the processor in response to the interrupt request from the external component. A signal processing circuit coupled to the second circuitry suppresses transmission of the interrupt request signal to the processor until the signal is transmitted to the processor.

Abstract: A programmable arbiter providing for dynamic configuration of prioritization schemes is implemented using a simple, but effective structure. One or more arbiter banks are structured in a cascading manner. Each arbiter bank receives a predetermined number of the set of bus requests to be arbitrated. Each bank is separately programmed to provide a rotating or fixed priority scheme to evaluate the priority of the bus requests. Thus by separately programming the arbiter banks to operate in a fixed priority or rotating priority manner, a flexible, programmable arbiter is created which can operate according to a fixed, rotating or hybrid priority scheme and is adaptable to a variety of applications.