Abstract: A host bridge having a plurality of pre-defined registers used for injecting errors to a selected device so that other devices are not affected and normal systems operations can continue is disclosed. In accordance with the method and system of the present invention, device select lines from each device are brought into the host bridge individually for determining if an error is to be injected to a selected device. First, a register or a bit in a register in the host bridge is matched against an incoming bus operation for the type of bus operation, a load or a store, to inject the error upon. Next, a register having an initial or random value within the host bridge indicates which occurrence of the operation to inject the error. If the value of the register indicates that an error is to be injected, the load or store operation is delayed by forcing zero byte enables until the device identifier of the selected device may be checked against a device register within the host bridge.

Abstract: A method and apparatus is provided in which I/O data is tagged to identify an ordering of data transfer requests relative to other data transfer requests. Write and Read transaction requests are tagged for ordering relative to previous write requests. Current read and write transaction requests are selectively allowed to bypass earlier write transaction requests which have been temporarily delayed in transfer. In one embodiment, the bypass occurs in a bridge buffer positioned between I/O devices and a system memory. In another embodiment, the methodology is applied where a split read or write transaction includes reserved bits in the attribute fields which are utilized to indicate if the transaction is allowed to bypass previous write transactions.

Abstract: A bus bridge including a buffer pool comprised of a first and a second buffer sets. The first and second buffer sets are associated with first and second peripheral devices respectively. The bridge is configured to receive an interrupt and identify the interrupt source. A buffer set associated with the interrupt source is selected and transactions in the selected buffer set flushed prior to forwarding the interrupt to a processor. The bridge is preferably configured to identify the interrupt source by receiving a first interrupt signal from the first peripheral device and a second interrupt signal from the second peripheral device. Preferably, the bridge is configured to flush the transactions by pushing them into system memory via a primary bus such as a host bus of a processor.

Abstract: A method and system for supporting multiple Peripheral Component Interconnect (PCI) local buses through a single PCI host bridge having multiple PCI interfaces within a data-processing system are disclosed. In accordance with the method and system of the present invention, a processor and a system memory are connected to a system bus. One or more PCI local buses are connected to the system bus through a single PCI host bridge having bus and frequency control logic and bus clocks. The PCI local buses include sets of in-line electronic switches, dividing each PCI local bus into PCI local bus segments for supporting more PCI peripheral component slots then are called out by the PCI local bus standard. The sets of in-line electronic switches are open and closed in accordance with the bus and frequency control logic within the PCI host bridge thereby allowing the PCI peripheral component slots to operate at different bus frequencies, including bus frequencies higher than 66 MHz by using the bus clocks.

Abstract: A methodology and implementing system are provided in which pipelined read transfers or PRTs are implemented. The PRTs include a request phase and a response phase. The PRT request phase involves a PRT request master delivering to a PRT request target, a source address, a destination address and the transfer size for the data being requested. In the PRT response phase, the PRT request target becomes a PRT response master, i.e. a PCI bus master, and initiates a completion of the transaction that was requested in the originating PRT request.

Abstract: In an electrical interface providing a predefined number of connections at least some of which have predefined functions and at least some of which have reserved, undefined or non-critical functions, selective use of at least one of the connections having a reserved, undefined or non-critical function is accomplished. At least one switch is provided which is controllable and coupled to switch at least one connection having a reserved, undefined or non-critical function to a desired customized function. In this way, the electrical interface can be selectively switched to provide additional functionality using reserved, undefined or non-critical connections of the interface.

Abstract: Method and system aspects for enhancing a peripheral component interconnect (PCI) bus to achieve higher frequencies of operation are described. A system aspect includes at least one source synchronous strobe line for providing a source synchronous strobe signal, and at least one PCI compliant device for driving the source synchronous strobe signal to clock data and address on and off a PCI bus, wherein a cycle time for data transactions is reduced. With the present invention, significantly higher frequency capability of PCI is enabled by defining a different clocking signal and protocol for clocking data on and off the bus. A very significant timing budget savings results through the use of a source synchronous strobe for clocking data. Cycle time for bus transactions is therefore reduced, so that the frequency of operation for a synchronous bus is increased.

Abstract: A method and implementing computer system is provided in which PCI bus load conditions are detected and dummy loads are selectively switched into the PCI bus under light load conditions in order to avoid voltage overshoot problems. Load control logic receives input signals representative of the presence or absence of adapters connected into PCI slots. The load control logic is connected to load control switches. The load control switches are arranged to selectively connect to the PCI slot or to a dummy load. The load control system is selectively operable, by controlling the load switches, to connect dummy loads into empty PCI slots to dampen the bus when light load conditions are detected to exist on the PCI bus. In a PCI system hot plug environment, the system is operable to quiesce the slot being hot plugged so that the adapter can be removed or inserted into a PCI slot while maintaining acceptable PCI bus loading conditions.

Abstract: Device selects lines from each I/O device are brought into a PCI host bridge individually so that the device number of a failing device may be logged in an error register when an error is seen on the PCI bus. Until the error register is reset, subsequent load and store operations are delayed until the device number of the subject device may be checked against the error register. If the subject device is a previously failing device, the load/store operation to that device is prevented from completing, either by forcing bad parity or zeroing all byte enables. By forcing bad parity of zero byte enables, the I/O device will respond to the load or store request by activating its device select line, but will not accept store data. Operations to devices which are not logged in the error register are permitted to proceed normally, as are all load store operations when the error register is clear.

Abstract: A bus bridge coupled between primary and secondary busses including a buffer pool with first and second buffer sets and steering logic configured to direct transactions received from first and second peripheral devices to the first and second buffer sets respectively. The bridge is configured to push posted memory write transactions posted in the first buffer set onto the primary bus ahead of and in response to a read request transaction from the first peripheral device while leaving transactions in the second buffer set unaffected. In one embodiment, the steering logic is configured to receive first and second grant signals produced by arbitration logic of the bridge. The first and second grant signals indicate mastership of the secondary bus and the source of a subsequent transaction to be received via the secondary bus. The bridge and the secondary bus are suitably compliant with the PCI protocol. The primary bus may be the host bus of a processor unit or a peripheral bus such as a PCI bus.

Abstract: A method and system for a merchandise checkout system utilizes a remote scanning device, a shopping cart and bags for allowing a purchaser to buy merchandise unassisted by store personnel. The remote scanning device reads product identity information from coded levels on products chosen by the purchaser and sends the information to a central processor. The central processor has a memory, which indexes price information and weight for each product based on the product identity information. The central processor sends an accumulated price and weight transaction to the remote scanning device for the purchaser's use. The product identity information on the products further include a security tag device which is deactivated by the remote scanning device.

Abstract: A peripheral interconnect for a computer system comprising a bridge, a peripheral bus, and a peripheral device, wherein at least one of these components is adapted to selectively operate in either a high performance mode or a low performance mode, the high performance mode using a first operating speed and a first protocol, and the low performance mode using a second operating speed which is lower than said first operating speed, and a second protocol which is different from the first protocol. The disclosed embodiment provides a high performance mode with a 100 MHz speed and a protocol that disallows pacing, and a low performance mode that uses a 66 MHz or 33 MHz speed and a standard PCI protocol that allows pacing. The high performance operating speed can be twice the low performance operating speed, by doubling the clock frequency and clocking data on only one clock edge, or by clocking data on both a rising edge and a falling edge of a clock signal while operating at the lower clock frequency.

Abstract: A method and system for supporting multiple Peripheral Component Interconnect (PCI) local buses through a single PCI host bridge having multiple PCI interfaces within a data-processing system are disclosed. In accordance with the method and system of the present invention, a processor and a system memory are connected to a system bus. First and second PCI local buses are connected to the system bus through a PCI host bridge. The first and second PCI local buses have sets of in-line electronic switches, dividing the PCI local buses into PCI local bus segments supporting a plurality of PCI peripheral component slots for connecting PCI devices. The sets of in-line electronic switches are open and closed in accordance with bus control logic within the PCI host bridge allowing up to fourteen or more PCI peripheral component slots for connecting up to fourteen PCI devices to have access through a single PCI host bridge to the system bus.

Abstract: A data processing system includes a processor, system memory and a number of peripheral devices, and one or more bridges which may connect between the processor, memory and peripheral devices and other hosts or peripheral devices such as in a network. A bridge, such as a PCI host bridge, connects between a primary bus (e.g system bus) and a secondary bus. The host bridge provides a dual host bridge function which creates two secondary bus interfaces. This allows increased loading capability under one dual host bridge compared to a lesser number of slots allowed under one normal host bridge. Also included is additional control logic for providing arbitration control and for steering transactions to the appropriate bus interface. Additionally, peer to peer support across the two secondary bus interfaces in provided.

Abstract: A method and implementing computer system is provided in which PCI bus load conditions are detected and dummy loads are selectively switched into the PCI bus under light load conditions in order to avoid voltage overshoot problems. Load control logic receives input signals representative of the presence or absence of adapters connected into PCI slots. The load control logic is connected to load control switches. The load control switches are arranged to selectively connect to the PCI slot or to a dummy load. The load control system is selectively operable, by controlling the load switches, to connect dummy loads into empty PCI slots to dampen the bus when light load conditions are detected to exist on the PCI bus. In a PCI system hot plug environment, the system is operable to quiesce the slot being hot plugged so that the adapter can be removed or inserted into a PCI slot while maintaining acceptable PCI bus loading conditions.

Abstract: A method and apparatus are provided in which a control scheme is implemented to enable a PCI bus to operate more than two PCI slots into which PCI devices may be installed. The PCI slots are checked to determine if a PCI device is installed in the slots and the speed at which the installed PCI devices are capable of running. If any of the slots has a 33 MHz device installed in any of the slots, the system is enabled to run more than two slots, and all of the PCI devices will run at 33 MHz. When no 33 MHz cards or devices are installed in the PCI slots, and PCI devices are only installed in the first two slots, then the system is enabled to run only the first two slots at the speed of 66 MHz. In one alternative embodiment, a default configuration routine sets the PCI bus speed at one of the operating frequencies and modifies that default if it is determined during a system configuration cycle that another speed is more appropriate.

Abstract: A method and implementing computer system is provided in which PCI CONFIG.sub.-- ADDRESS and CONFIG.sub.-- DATA conventions are maintained in a large computer system and each PCI Host Bridge (PHB) CONFIG.sub.-- ADDRESS register and each PHB CONFIG.sub.-- DATA register have separate and system-unique addresses. In one example, the operating system provides a service to translate the device driver's configuration operation to a particular bus and device in the system, to a particular CONFIG.sub.-- ADDRESS or CONFIG.sub.-- DATA register of the PHB which has that device under it. By using this method, the hierarchical system can use architecture-independent routing of addresses down to the PHB that contains the appropriate CONFIG.sub.-- ADDRESS and CONFIG.sub.-- DATA registers.

Abstract: A method and implementing system are provided which includes a PCI host bridge connected to a PCI bus. The PCI slots are applied to a switch array which is controlled by circuitry within the PCI host bridge in the example. The switch array is connected to interrupt control logic which is, in turn, coupled to the PCI host bridge. The methodology in one example uses the Interrupt Pin field in the PCI configuration space currently supported by the PCI Specification to identify an ISA interrupt signal line to which a migrated ISA device needs to be connected. Migrated ISA devices in PCI card connectors are then identified by determining the interrupt information associated with the ISA interrupt signal line identification method used. An interrupt switch array is then used to connect the migrated ISA device interrupt to the desired IRQx signal line and to the interrupt control logic. The switching array provides for a translation of PCI to ISA interrupts for connection to an interrupt controller.

Abstract: A method and system for supporting multiple Peripheral Component Interconnect (PCI) local buses through a single PCI host bridge having multiple PCI interfaces within a data-processing system are disclosed. In accordance with the method and system of the present invention, a processor and a system memory are connected to a system bus. First and second PCI local buses are connected to the system bus through a PCI host bridge. The first and second PCI local buses have sets of in-line electronic switches, dividing the PCI local buses into PCI local bus segments supporting a plurality of PCI peripheral component slots. The sets of in-line electronic switches are open and closed in accordance with bus control logic within the PCI host bridge allowing up to fourteen PCI peripheral component slots to have access through a single PCI host bridge to the system bus.

Abstract: A system of supporting differential signalling circuitry in an enhanced PCI bus within a data processing system is disclosed The enhanced PCI bus comprises a plurality of differential signal conductor pairs. A system and method in accordance with the present invention comprises a system for providing each of the plurality of differential signal pairs over a first line and a second line, the first line having a front end and a back end, the second line having a front end and a back end. The system and method includes a differential driver for driving the first line and the second line with a small voltage change of equal amounts in opposite direction to change logic states, a receiver for sensing a voltage change between the first line and the second line and a termination network coupled to the first line and second line for terminating the first line and the second line.