Abstract: The present invention is directed to a method and apparatus for performing exchange transactions between caches and a main memory of a computer system, the caches and main memory being coupled to one another by a bus. The method includes the steps of providing caches of different sizes with a cache having a smallest size, and with each cache having an index fixed as a function of the size of the cache. For each exchange transaction, the number of bits of an index used to address a selected cache location are determined, and the upper bits of a memory address from a tag store location corresponding to the selected cache location are retrieved, where the retrieved upper address bits form an exchange address. In the event that the index of the selected cache location comprises more bits than the index of the cache having the fewest addressable locations, the excess bits of the index of the selected cache location are appended to the exchange address.

Abstract: The present invention is directed to a computer apparatus for use in a multiprocessor computer system having a main memory storing a plurality of data items and being coupled to a bus. The bus is operated according to a SNOOPY protocol. The computer apparatus includes a processor and a cache memory coupled to the processor. The cache memory contains a subset of the data items stored in the main memory, for access by the processor and includes a TAG store comprising a plurality of VALID indicators, one VALID indicator for each of the data items currently contained in the cache memory. A bus interface is coupled to the cache memory and is adapted for coupling to the bus. The interface operates according to the SNOOPY protocol to monitor transactions on the bus for write transactions affecting data items of the subset having set VALID indicators and determines the identity of each initiator of a write transaction on the bus affecting a VALID data item of the subset.

Abstract: A computer system includes a processor having a primary cache, and a secondary cache data store, cache tag store, and memory controlled by a memory controller. The cache tag store, secondary cache data store, and memory share a common address bus. The secondary cache data store and the memory share a common data bus. In addition, some of the bits of the address bus are saved and fed directly to the memory. The memory controller provides for pipelined secondary cache accesses, during which a corresponding tag from the cache tag store is compared in the processor against the required memory address to determine if the data is located in the secondary cache. If the data is not in the secondary cache, the memory controller asserts the appropriate signals to obtain the data from memory. Because some of the address bits are fed directly to the memory, the setup time for memory control signals can be satisfied during the comparison of the cache data tag.

Abstract: A method for providing communication between a plurality of nodes coupled in a ring arrangement, wherein a plurality of the nodes comprise processors each having a cache memory for storing a subset of shared data. Each of the nodes on the ring deposits data into a data slot during a given time period. The data deposited by each node may comprise an address field and a node field. To ensure data coherency between the caches, each processor on the ring includes a queue for saving a plurality of received data representative of the latest bus data transmitted on the bus. As each processor receives new data, the new data is compared against the plurality of saved data in the queue to determine if the address field of the new data matches the address field of any of the saved data of the queue. In the event that the new data matches one of the plurality of saved data, it is determined whether the new data represents updated data from the memory device.

Abstract: A data storage system includes a multi-tasking processor which manages a write cache to identify adjacent blocks held in the write cache which are to be included in a next write operation, while at the same time handling data transfer requests from a system host. The processor monitors the write cache and when the cache has fewer than a predetermined number of storage locations free, initiates a block-merge task. The processor then determines which block in the write cache is least recently used and, based on virtual block numbers assigned to the data blocks, identifies the blocks in the write cache which are adjacent to the least recently used block and are within the same chunk as that block. The processor maintains a list of these adjacent blocks and the locations in which the blocks are held in the write cache.

Abstract: A semiconductor memory device according to the invention includes a main memory array comprising a plurality of memory sub-arrays. Each of the memory sub-arrays comprises a plurality of columns and at least one redundant column. Each column of the memory sub-array also includes multiplexing means, coupled to the input and output path of the respective column and an input and output path of a neighboring column. In addition, the redundant column is coupled to the input and output path of a neighboring column. In the event that one of the columns of the memory sub-array is defective, the multiplexing means of each of the columns between the defective column and the redundant column acts to couple the input and output paths of that column to the input and output paths of the neighboring column. With such an arrangement, the defective column is bypassed and a memory device capable of operating without defects is provided.

Abstract: This invention relates to an image processing system which relies upon quantization and dithering techniques to enable an output device, which has a given number of output levels, to accurately reproduce a image which is generated by an input device, which has a greater or equal number of input levels. Generally, neither the number of input nor output levels need to be a power of two. The present invention is implemented in a number of different embodiments. These embodiments generally rely upon an image processor which, depending on the particular implementation, includes memory devices and an adder, a comparator, or a bit shifter. Additional embodiments use an image adjustment system to refine the raw input levels of the input device, in order to create an improved output image. Also, the particular embodiments of the image processors can be used in connection with imaging systems having bi-tonal, monochromatic, or color input and output devices.

Abstract: A fault tolerant computer according to the invention includes a processing unit including a first processor coupled to a first system bus to provide data to a cache and a memory, and a second processor coupled to the first system bus and a second, abbreviated system bus to receive read data from said first system bus. Coupled to said processing unit is an Input/Output device for interfacing to external devices. The processing unit includes a phase detector apparatus for aligning a clock of the processor unit to that of the Input/Output unit to facilitate data transfer. The phase detector apparatus includes a first means for providing a first clocking signal related to the clocking signal of the Input/Output unit, and a second means for providing a second clocking signal related to the clocking signal of the processor unit. The phase detector apparatus further includes means for providing an error signal responsive to an offset between edges of the first and second clocking signals.

Abstract: An apparatus for dithering an input image to produce an output array for representation on an output device is described. The apparatus includes an input device to store input image pixels having a first plurality of chrominance or luminance levels; a dithering system including a dither template including an M by N matrix of integer threshold values, the uniform distribution of threshold values throughout the dither template possessing homogeneous attributes. The apparatus further includes a normalizer unit for normalizing the threshold values of the dither template for storage in a dither matrix according to the first plurality of chrominance or luminance levels of the input image pixels and a second plurality of chrominance or luminance levels of the output array and a summation unit to add the input image pixel chrominance or luminance values to the normalized threshold values of the dither matrix.

Abstract: A pipelined processor includes an instruction unit including a register mapper, to map register operand fields of a set of instructions and an instruction scheduler, fed by the set of instructions, to reorder the issuance of the set of instructions from the processor. The mapped register operand fields are associated with the corresponding instructions of the reordered set of instructions prior to issuance of the instructions. The processor further includes a branch prediction table which maps a stored pattern of past histories associated with a branch instruction to a more likely prediction direction of the branch instruction. The processor further includes a memory reference tagging store associated with the instruction scheduler so that the scheduler can reorder memory reference instructions without knowing the actual memory location addressed by the memory reference instruction.

Abstract: This invention relates to an image processing system which relies upon quantization and dithering techniques to enable an output device, which has a given number of output levels, to accurately reproduce a image which is generated by an input device, which has a greater or equal number of input levels. Generally, neither the number of input nor output levels need to be a power of two. The present invention is implemented in a number of different embodiments. These embodiments generally rely upon an image processor which, depending on the particular implementation, includes memory devices and an adder, a comparator, or a bit shifter. Additional embodiments use an image adjustment system to refine the raw input levels of the input device, in order to create an improved output image. Also, the particular embodiments of the image processors can be used in connection with imaging systems having bi-tonal, monochromatic, or color input and output devices.

Abstract: A semiconductor memory device according to the invention includes a main memory comprising a number of memory sub-arrays, each coupled to an address and a data bus, for providing or receiving data to an intermediate interface unit. The intermediate interface unit provides data to and receives data from an output bus. Also included in the semiconductor memory device is redundancy circuit including a redundant memory coupled to the output bus for storing a subset of data from one of the sub-arrays in the event that the sub-array is defective. The redundancy circuit additionally includes address fuses for storing the sub-array addresses of the subset of data to be stored in the redundant storage, and compare circuitry coupled to the address bus for comparing the address bus to the stored array addresses to determine if there is a match.

Abstract: This invention relates to an image processing system which relies upon quantization and dithering techniques to enable an output device, which has a given number of output levels, to accurately reproduce a image which is generated by an input device, which has a greater or equal number of input levels. Generally, neither the number of input nor output levels need to be a power of two. The present invention is implemented in a number of different embodiments. These embodiments generally rely upon an image processor which, depending on the particular implementation, includes memory devices and an adder, a comparator, or a bit shifter. Additional embodiments use an image adjustment system to refine the raw input levels of the input device, in order to create an improved output image. Also, the particular embodiments of the image processors can be used in connection with imaging systems having bi-tonal, monochromatic, or color input and output devices.

Abstract: In general, in one aspect, the invention features a fastener having two mating pieces. One of the mating has a rigid surface of thickness q, and a hole in the surface, the hole including a slot defined by two generally parallel edges separated by a distance r. The other mating piece has a base and a pair of wings held above the base to define two generally parallel channels spaced to accommodate the two parallel edges of the slot, the channels having a thickness greater than q, the span of the wings being greater than r.

Abstract: A fault-tolerant computer system has primary and backup computers. Primary and backup virtual machines running on the computers are controlled by corresponding virtual machine monitors. The virtual machines execute only user-mode instructions, while all kernel-mode instructions are trapped and handled by the virtual machine monitors. Each computer has a recovery register that generates a hardware interrupt each time that a specified number of instructions, called an epoch, are executed. Prior to failure of the primary computer, the backup computer's virtual machine monitor converts all I/O instructions into no-ops and the primary computer sends copies of all I/O interrupts to the backup computer.

Abstract: An I/O bus interface cell includes a driver circuit having an input terminal fed by a logic signal and an output terminal to produce in response thereto a drive signal having selectable rise and fall time characteristics in accordance with a reference voltage provided to the driver. The I/O cell also includes a receiver circuit having an input terminal coupled to said output terminal of said driver with the receiver disposed to latch an unresolved, unamplified received signal prior to resolving the state of the signal. The I/O cell further includes a termination circuit having a terminal connected to the output of said driver, and having a selectable impedance characteristic at said terminal, with said selectable impedance being in accordance with a reference voltage provided to an input of said termination circuit. Preferably, the I/O cell the driver, receiver and termination circuits are fabricated on a common semiconductor substrate.

Abstract: A cash pocket for an automatic teller machine (ATM) comprises a housing having a rear wall with a slot for receiving banknotes from the dispensing mechanism of the ATM into the housing, and a base upon which the dispensed banknotes come to lie upon being dispensed into the housing. The housing also has a front panel having an opening for the withdrawal of notes by a user of the ATM, the opening having a door which pivots about an axis substantially parallel to the longitudinal axis of the slot from a first position in which the front opening is closed to a second position in which the front opening is open for the withdrawal of dispensed banknotes. The door includes a pair of flanges which block access to the slot from the front opening when the door is open or partially open.

Abstract: A high-performance central processing unit (CPU) of the reduced instruction set (RISC) type employs a standardized, fixed instruction size, and permits only simplified memory access data width and addressing modes. The instruction set is limited to register-to-register operations and register load/store operations. The processor can employ a variable memory page size, so that the entries in a translation buffer for implementing virtual addressing can be optimally used. A granularity hint is added to the page table entry to define the page size for this entry.

Abstract: A pipelined processor has an instruction unit for decoding instructions and pre-processing operands prior to instruction execution, and an execution unit for executing the decoded instructions. The pre-processing of operands includes changes to general purpose registers, and the changes are recorded in an RLOG queue having read and write pointers. Instruction context for the RLOG queue entries is maintained in a separate RLOG base queue. When decoding begins for a new instruction, the RLOG base queue is loaded with the RLOG write pointer to the first RLOG queue entry that would record a register change for that next instruction. Each time an operand is processed that changes a general purpose register, the value of the change is recorded in the entry pointed to by the RLOG queue write pointer, and the RLOG queue write pointer is advanced.

Abstract: A method of testing an integrated circuit having a plurality of pins includes the steps of providing a functional test set having an ordered group of test strings wherein each element of the test string is related to one of the pins of said integrated circuit. The group of test strings is searched to locate a sequence of test strings having a undesirable pattern. The undesirable pattern can be a pattern in which none of the elements associated with the test string changes or a pattern in which a reference element and at least one other element of the test string changes. When a sequence of test strings having the undesirable pattern is located, the group of test strings is processed to correct the undesirable pattern. When all the vector sequences having an undesirable patterns are corrected, the group of test vectors is applied to the input pins of the integrated circuit.