Patents Represented by Attorney Denis G. Maloney
  • Patent number: 5544179
    Abstract: A transmitting node generates error correction symbols by encoding data using error correction code integrated with information which identifies the data cycle in which the data are to be transmitted, the integrated encoded data having the same number of bits as the error correction code has alone. A node receiving the data generates error correction symbols encoding the received data using error correction code integrated with information which identifies the data cycle in which the receiving node is operating. A comparison is made of the transmitting node error correction symbols received with the receiving node generated error correction symbols, and if the two sets of symbols do not match, the receiving node detects and, if possible, corrects errors in the data using the error correction code. Alternatively, the receiving node may remove the data cycle information from the received error correction symbols and perform a comparison using standard error correction code applied to the received data.
    Type: Grant
    Filed: February 1, 1995
    Date of Patent: August 6, 1996
    Inventor: David Hartwell
  • Patent number: 5543936
    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.
    Type: Grant
    Filed: October 15, 1992
    Date of Patent: August 6, 1996
    Assignee: Digital Equipment Corporation
    Inventor: Robert A. Ulichney
  • Patent number: 5542058
    Abstract: A macropipelined microprocessor chip adheres to strict read and write ordering by sequentially buffering operands in queues during instruction decode, then removing the operands in order during instruction execution. Any instruction that requires additional access to memory inserts the requests into the queued sequence (in a specifier queue) such that read and write ordering is preserved. A specifier queue synchronization counter captures synchronization points to coordinate memory request operations among the autonomous instruction decode unit, instruction execution unit, and memory sub-system. The synchronization method does not restrict the benefit of overlapped execution in the pipelined. Another feature is treatment of a variable bit field operand type that does not restrict the location of operand data. Instruction execution flows in a pipelined processor having such an operand type are vastly different depending on whether operand data resides in registers or memory.
    Type: Grant
    Filed: October 4, 1994
    Date of Patent: July 30, 1996
    Assignee: Digital Equipment Corporation
    Inventors: John E. Brown, III, G. Michael Uhler, John H. Edmondson, Debra Bernstein
  • Patent number: 5539345
    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.
    Type: Grant
    Filed: December 30, 1992
    Date of Patent: July 23, 1996
    Assignee: Digital Equipment Corporation
    Inventor: Thomas B. Hawkins
  • Patent number: 5537575
    Abstract: A method and apparatus in a computer system for handling cache memory victim data for updating main memory. The invention operates in a computer system having one or more processor modules coupled to main memory by a system bus operating in accordance with a SNOOPING bus protocol. Upon a processor executing a READ of one of the cache memory addresses, cache memory data corresponding to the cache memory address being READ is transmitted into the data interface from the cache memory data storage. The cache memory data is received accumulatively by the data interface during the execution of the READ of the cache memory address information. A determination is made as to whether the cache memory data corresponding to the cache memory address being READ is a cache memory victim. If the determination establishes that it is a cache memory victim, the processor issues a command for transmitting cache memory victim data to main memory over the system bus.
    Type: Grant
    Filed: June 30, 1994
    Date of Patent: July 16, 1996
    Inventors: Denis Foley, Douglas J. Burns, Stephen R. Van Doren
  • Patent number: 5534811
    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.
    Type: Grant
    Filed: June 18, 1993
    Date of Patent: July 9, 1996
    Assignee: Digital Equipment Corporation
    Inventors: William B. Gist, Joseph P. Coyle
  • Patent number: 5535020
    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.
    Type: Grant
    Filed: October 15, 1992
    Date of Patent: July 9, 1996
    Assignee: Digital Equipment Corporation
    Inventor: Robert A. Ulichney
  • Patent number: 5535392
    Abstract: A method and system for compiling a source program using smart recompilation. The invention allows fragments to contain "invocation specific" information, which is generated during a code generation phase of compilation. A hint generator attempts to preserve values of the invocation specific information between successive invocations of the compiler.
    Type: Grant
    Filed: March 10, 1995
    Date of Patent: July 9, 1996
    Assignee: Digital Equipment Corporation
    Inventor: Bevin R. Brett
  • Patent number: 5532918
    Abstract: A high-power-factor power supply has a full-wave rectifier for rectifying an AC line voltage, a power regulator including switch means responsive to a control signal for controlling the application of the rectifier output to a load; and a control circuit for producing a switching control signal. The control signal includes a pair of AC line detectors: a first connected in a closed-loop automatic gain control arrangement, and the other connected in an open-loop arrangement. The control circuit initially produces a CURRENT DEMAND REFERENCE signal that is directly related to the difference between the power supply DC output voltage and a self-generated constant reference, and to the waveform shape of the AC line voltage, and is inversely related to magnitude changes of the AC line voltage. The control signal then produces the switching control signal in response to both the CURRENT DEMAND REFERENCE signal and the current flowing in the power supply.
    Type: Grant
    Filed: April 14, 1994
    Date of Patent: July 2, 1996
    Assignee: Digital Equipment Corporation
    Inventors: James F. Mayrand, James Gregorich
  • Patent number: 5533195
    Abstract: A flexible software testing tool provides fast and efficient diagnosis of defective computer system devices. The software testing tool includes an action string command qualifier that enables dynamic exercising of target computer devices by specifying certain operations involving those devices. Additional command qualifiers are provided to define the operating conditions of the device interaction paths. The operations specified by the qualifiers typically require interactions between a plurality of devices, thereby creating combinations of device interaction paths within the system to detect intermittent device failures.
    Type: Grant
    Filed: March 6, 1995
    Date of Patent: July 2, 1996
    Inventors: Paul E. LaRochelle, Arthur J. Beaverson
  • Patent number: 5528605
    Abstract: A computer communications system has a controller for controlling a master with a circuit timer, the circuit timer is capable of aggregating data produced during a circuit timer interval into a single master message, and the data is produced by a plurality of users, where each user is capable of establishing a plurality of sessions. There is a communication pathway, responsive to expiration of the circuit timer interval, for sending the aggregated data to a slave. Also there is a acknowledgement circuit for the slave to send an acknowledge message to the master upon expiration of a delay ACK time interval, the delay ACK time interval is greater than the circuit timer interval, and the circuit timer is capable of initiating sending of a plurality of master messages during one delay ACK time interval.
    Type: Grant
    Filed: October 25, 1994
    Date of Patent: June 18, 1996
    Assignee: Digital Equipment Corporation
    Inventors: John A. Ywoskus, Bruce E. Mann, Kenneth J. Izbicki, Roger H. Levesque
  • Patent number: 5525829
    Abstract: A MOSFET device is constructed with an integrated Schottky diode clamp connected between the source or drain terminal and the bulk terminal. In an illustrative implementation, one or more MOSFETs are formed in an n-well located in a p-type silicon substrate. Each drain is formed by a p+ region underlying a portion of a metal-silicide layer. In one embodiment, the p+ region underlies an edge of the metal-silicide; in another embodiment, the p+ region underlies opposing edges of the metal-silicide, such that a portion of the metal-silicide contacts the n-well. Each source is formed by a p+ region underlying a layer of metal-silicide. Each gate includes a layer of p+ or n+ polycrystalline silicon clad with a layer of metal-silicide, the gates being separated from the n-well by a layer of oxide. In comparison to p-n junction diodes, the integrated Schottky diodes more effectively limit excess voltages applied to MOSFETs.
    Type: Grant
    Filed: February 28, 1994
    Date of Patent: June 11, 1996
    Assignee: Digital Equipment Corporation
    Inventor: Kaizad R. Mistry
  • Patent number: 5526477
    Abstract: A method and apparatus for generating glyphs for text elements input to a computer having a memory with at least one look-up table storing glyphs corresponding to such text elements. Each text element is made up of at least one code point, and often of several code points. The system searches the table for a glyph representing an input text element, and if it is not found methodically generates subsets of the text element and searches the table for glyphs representing each of the subsets. Default characters are generated for code points not represented in the table. The system uses a classification for each code point, such as the Unicode classifications, and handles unknown code points in a manner dependent upon their classification. Where a text element includes two characters with an intermediate joining character, and the text element as a whole is not represented in the table, the two characters are output for rendering separately.
    Type: Grant
    Filed: January 4, 1994
    Date of Patent: June 11, 1996
    Assignee: Digital Equipment Corporation
    Inventors: John I. McConnell, Mordehai Huberman
  • Patent number: 5519841
    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.
    Type: Grant
    Filed: November 12, 1992
    Date of Patent: May 21, 1996
    Assignee: Digital Equipment Corporation
    Inventors: David J. Sager, Simon C. Steely, Jr., David B. Fite, Jr.
  • Patent number: 5517660
    Abstract: Read-write buffer apparatus is provided for reducing the time necessary to resolve read conflicts during normal and block mode read requests. Additionally, the read-write buffer apparatus provides a means for gathering non-sequential write requests in an internal write buffer, thus reducing the frequency of a buffer full condition. The enhanced read-write buffer apparatus minimizes CPU wait states, while increasing the CPU processing rate and improves overall data processing system throughput.
    Type: Grant
    Filed: September 12, 1994
    Date of Patent: May 14, 1996
    Assignee: Digital Equipment Corporation
    Inventor: Mitchell N. Rosich
  • Patent number: 5515523
    Abstract: A method for arbitrating conflicting requests for a memory transfer in a multiport memory system including first and second memory ports. The method includes the following steps. First, monitoring the volume of memory transfer requests from the first memory port. Second, partially disabling the second memory port if the memory request volume is greater than a first predetermined volume. And third, reenabling the second memory port when the memory request volume becomes less than a second predetermined volume. Apparatus implementing this method which includes an activity detector, coupled to the first memory port, for generating a bistate signal having a first state when the volume of memory requests by the first memory port exceeds a first predetermined volume and a second state otherwise. Circuits are provided for selectively partially disabling memory requests from the second memory port in response to the bistate signal being in the second state.
    Type: Grant
    Filed: August 10, 1994
    Date of Patent: May 7, 1996
    Assignee: Digital Equipment Corporation
    Inventors: Ramsesh Kalkunte, Satish Rege, Ronald Edgar
  • Patent number: 5508558
    Abstract: An interconnect structure formed of a flexible, multilayer dielectric material such as polyimide, having a support ring, connection points on the section inside the support ring for connecting one or more semiconductor chips, and connection points outside the support ring for connecting to a circuit board. Alignment templates are disclosed which align the semiconductor chip with the connection points.
    Type: Grant
    Filed: October 28, 1993
    Date of Patent: April 16, 1996
    Assignee: Digital Equipment Corporation
    Inventors: William C. Robinette, Jr., Chung W. Ho
  • Patent number: 5508822
    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.
    Type: Grant
    Filed: October 15, 1992
    Date of Patent: April 16, 1996
    Assignee: Digital Equipment Corporation
    Inventors: Robert A. Ulichney, Paramvir Bahl
  • Patent number: 5500947
    Abstract: A method of specifying the operands for a microcoded CPU employs a combination of a set of microinstruction routines for generic operand modes, along with hardware primitives for selecting various specific types of operand treatment. Decoding of a machine-level instruction produces an entry point for the microstore, selecting one of the set of generic operand modes. Also, decoding of the instruction produces control bits that are used directly to select the specific operand type or used by the hardware primitives. In this way, branching is avoided in the microinstruction sequences used for operand specifying, but yet the amount of microcode needed is a minimum.
    Type: Grant
    Filed: July 1, 1994
    Date of Patent: March 19, 1996
    Assignee: Digital Equipment Corporation
    Inventors: George M. Uhler, John F. Brown, III
  • Patent number: 5499364
    Abstract: A distributed computation system has a set of agents that perform each specified distributed computation. State transition events in each agent are conditioned or dependent on state transition events in other ones of the agents participating in the same distributed computation. The event dependencies between events in the agents are dynamically specified at run time from a set of predefined dependency types. The assigned conditions for resolving the truth value of these events are stored in local knowledge databases in each of the agents. Each agent stores in its local knowledge database a representation of the conditions for local events, which are state transition events in that agent, and a representation of the conditions for those external events that depend on notifications of local events in this agent and for those external events on which the local events are dependent. The local knowledge database also stores status information on the current truth value of the local and external events.
    Type: Grant
    Filed: October 14, 1993
    Date of Patent: March 12, 1996
    Assignee: Digital Equipment Corporation
    Inventors: Johannes Klein, Francis R. Upton, IV