Sgs-thomson Microelectronics Limited

Motorola Corporation

International Business Machines Corporation

Bahador Rastegar

Paul C Rossbach

David D Barrera

William C Slemmer

Dave Levitan

A memory cache (14) has a semi-associative cache array (50), a cache reload buffer (40), and a cache reload buffer driver (42). The memory cache writes received data to the cache reload buffer and waits until the data is requested again before it invalidates any cache aliased entries in the semi-associative cache array. This invalidation step requires no dedicated cycle but instead is a result of the memory cache being able to simultaneously read from the semi-associative cache array and the cache reload buffer.

Memory cache with automatic alliased entry invalidation and method of

A memory cache (14) has a plurality of cache lines (50) for storing a series of contiguous memory elements. Each series of memory elements are interlaced within the corresponding cache line on a element-by-element basis and on a bit-by-bit basis. This storage strategy allows the memory cache to output a subset memory elements within a cache line quickly and in the original contiguous order. The invention may be advantageously incorporated in an instruction cache of superscalar data processor to provide a series of sequential instructions for execution.

Memory cache with interlaced data and method of operation

A memory device provides a control circuit attached to a parity bit position of a memory array. When a selected single bit within an array entry has its value changed without affecting the remaining bits of the entry, the control circuit senses the previous value of the parity bit and internally stores the complement of that value into the parity bit position for that entry. This complementing of the parity bit occurs during the same memory cycle in which the selected bit is changed. Complementing of the parity bit to ensure proper parity function occurs without communication off of the device, and so is completely transparent to the outside world.

Control circuit for dual port memory

A push-pull output driver including two transistors in series, one transistor having its body bias controlled by logic circuitry commanded by the driver input. The driver has a pair of transistors in series, the transistor inputs being complementary to create a push-pull amplifier. A switching transistor is controlled by the inverse of the driver input signal and acts as a switch at the pull-up transistor well-tie. When the driver input is high, the switching transistor is off allowing the well-tie to the pull-up transistor to be connected to the driver output. When the input is low, the switching transistor turns on, switching the well-tie of the pull-up transistor to ground. By controlling the body bias of the pull-up transistor in this way, the switching speed of the output driver is significantly increased. When the output driver is in a disabled tri-state mode, the series transistors, and the switching transistor, are turned off. A first deselect transistor provides a high voltage at the drain of a load transistor to force it into cutoff. A select transistor is turned off to isolate the pull-up transistor well-tie from the output node, and a second deselect transistor is switched on to connect it to ground. This embodiment isolates the well-tie from the driver output while in tri-state to prevent latch-up initiated by multiple power supply operation.

Output driver circuit with body bias control for multiple power supply

A memory which is cleared by simultaneously clearing a special bit in each entry within the memory, an extra bit, used for other purposes, is also cleared. When both bits have a value of 0, parity checking is disabled. When either bit has a value of 1, parity checking is enabled. This prevents incorrect detection of parity errors after the memory device has been cleared.

Cache tag parity detect circuit

A control circuit for a dual port cache tag memory is used to reset a snoop valid bit for an entry addressed through one of the dual ports. This port snoops a main memory bus, and a cache tag hit which occurs during a write operation to the main memory bus indicates that the snoop valid bit for the addressed entry should be reset. In order to avoid errors in resetting the snoop valid bit, which errors can occur due to signal propagation delay, the control circuit resets the snoop valid bit only after a preselected internal delay period.

Control circuit for resetting a snoop valid bit in a dual port cache tag

A dual-port memory device provides bit lines having a crossover pattern to reduce stray end coupling capacitances. Such crossover occurs approximately in the middle of the memory array for the device. Data in one-half of the array is stored in an inverted manner from data in the other half of the array. A preferred technique for clearing a memory provides for resetting only a portion of the bits of the array for each entry, with the bits of all memory entries being reset simultaneously. In order to provide such a reset function with the preferred bit line crossover scheme, a voltage node used for reset must also provide signal lines which are crossed over in the middle of the array.

Integrated circuit memory device having flash clear

A dual-port memory device is provided which has a memory array divided approximately in half. The bit lines for the array are crossed over between array halves in order to minimize stray capacitance and cross-coupling capacitance for the device. Redundant rows are provided for the device which can be programmed to substitute for array rows containing non-functional bits. Preferably, the redundant rows are provided only in one-half of the array. The redundant rows can all be located in a first half of the array, with the second half of the array being the half which provides inverted data for one of the ports. If a redundant row replaces an array row in the second half of the array, and is written to by the port which reads and writes inverted data, the data must be reinverted prior to writing it to, or reading it from, the redundant row.

Integrated circuit memory device with redundant rows

A dual-port memory device provides for a memory array which is divided approximately in half. Between the two halves of the array, a bit line crossover scheme is provided which minimizes stray capacitance and cross-coupling capacitance between bit lines for the two different ports. A bit line layout plan which minimizes such capacitances causes the data for one of the ports to be inverted in one-half of the array. When data from this half of the array is read or written by such port, the data being read or written must be inverted.

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Dallas, TX, United States of America

Bahador Rastegar