International Business Machines Corporation

Cang Ngoc Tran

James Allan Kahle

Alfredo Aldereguia

Nader Amini

John Victor Sell

Richard Louis Horne

Douglas Christopher Hester

Daryl Carvis Cromer

Marlin Wayne Frederick, Jr

Bruce Joseph Ronchetti

Terence J Lohman

Ashu Kohli

Mark D Sweet

Dac C Pham

Kimberly Kibbe Sendlein

A system and method for determining an age function by performing a logical function on each entry residing within a queue, determining when a particular one of the entries residing in the queue was stored in the queue relative to the other entries, and determining an oldest or youngest entry residing in the queue relative to the logical functions performed on each of the instructions. In one embodiment of the present invention, the entries are instructions temporarily stored within a queue in the processor. The logical function performed may determine which of the instructions is valid. The queue may be cyclical.

System and method for determining the relative age of instructions in a processor

A method and system for input/output control in a multiprocessor system having multiprocessors coupled to a system memory via a common wide bus. The common wide bus is subdivided into multiple sub-buses which may be accessed individually or in groups by a selected processor, or individual sub-buses may be accessed by multiple processors simultaneously in response to one or more transfer requests. In response to a transfer request having a data address associated therewith, a particular target device is identified. The data address is then written into an address queue. Thereafter, one or more of the multiple sub-buses are utilized to transfer data to or from a single processor in response to a transfer request from a single processor. In response to a transfer request from multiple processors, one or more of the multiple sub-buses may be utilized separately to simultaneously transfer data to or from multiple processors.

Method and system for input/output control in a multiprocessor system

A method and system for arbitrating access to a component of a computer have been disclosed the method and system include an arbitration unit for granting access to the component; and a plurality of units for executing a plurality of transactions requiring access to the component. Each transaction of the plurality of transactions has an encoded priority. Each of the plurality of units further provide the arbitration unit with the encoded priority of each of the plurality of transactions. The arbitration unit grants a predetermined number of the plurality of units access to the component in response to the encoded priority of each of the predetermined plurality of transactions.

Selectable priority bus arbitration scheme

A method and system for enhanced bus access in a multiprocessor system having multiprocessors coupled to a system memory via a common wide bus. The common wide bus is subdivided into multiple sub-buses which may be accessed individually or in groups by a selected processor, or individual sub-buses may be accessed by multiple processors simultaneously. In response to one or more pending transactions, each processor outputs a request to bus arbitration logic for a maximum-permitted number of sub-buses. If the number of sub-buses granted to a particular processor equals the number of pending transactions at that processor, all pending transactions are performed in parallel on separate sub-buses. If the number of sub-buses granted is less than the number of pending transactions, pending transactions are performed in a priority order. Finally, if the number of granted sub-buses is greater than the number of pending transactions, selected transactions are performed over multiple sub-buses in parallel, greatly enhancing the speed of those transactions.

Method and system for simultaneous variable-width bus access in a

A method and system for enhanced bus arbitration in a multiprocessor system having multiprocessors coupled to a system memory via a common wide bus. The common wide bus is subdivided into multiple sub-buses which may be accessed individually or in groups by a selected processor, or individual sub-buses may be accessed by multiple processors simultaneously. In response to one or more pending transactions, each processor outputs a request to bus arbitration logic for a number of sub-buses. A maximum number of sub-buses is specified for each processor and the processors are prioritized. Each time a bus request is received from a processor, the number of requested sub-buses is granted, if that number is equal to or less than the specified maximum number of sub-buses for that processor. If the requested number of sub-buses is greater than the specified maximum number of sub-buses for that processor the requested number is granted if no other processor has issued a bus request.

Method and system for bus arbitration in a multiprocessor system

A method for maintaining memory coherency in a data processing system is disclosed. The data processing system includes a memory system having a dual bus memory controller, which is coupled to a first bus through a first bus master and a second bus coupled to a second bus master. The method maintains memory coherency by snooping across either the first or second bus for attributes on an address/data multiplex bus in the data processing unit. To determine when a snoop operation is required, the system begins by requesting access to either of the two buses through the dual bus memory controller. Once the control of the bus has been granted upon request data is transferred using the master bus controller. It is upon the receipt of an invalid data signal while transferring data across the bus that the snoop activity begins. The snoop is injected only after an invalid data signal is received and a last snoop injection can occur only before a last read data is read.

Method for maintaining memory coherency in a computer system having a

During a first cycle, data information is output through a bus from a device coupled to the bus. During a second cycle immediately after the first cycle, address information is output through the bus from the device.

System and method for communicating between devices

Circuitry within a processor delays the launching of data onto an external bus by a factor that is proportional to the ratio of an internal processor clock speed to the system or external bus clock speed. This delay provides a delay in the launching of data to external bus devices so that these slower speed external bus devices have enough time to capture the data.

Apparatus for delaying the output of data onto a system bus

A computer system is provided, comprising system memory and a memory controller which resides on a system bus for controlling access to the system memory, a bus interface unit and a direct memory access controller also residing on the system bus, and a central processing unit electrically connected with the memory controller which is able to read and write data to the system memory via the memory controller. The memory controller and the bus interface unit each operate, when either is in control of the system bus, at a clock frequency which is a multiple of the clock frequency at which the direct memory access controller operates on the system bus. The memory controller and the bus interface unit each operate, when the direct memory access controller is in control of the system bus, at the same clock frequency as that of the direct memory access controller. The clock frequencies of the memory controller, the bus interface unit and the direct memory access controller are each synchronized in time. The computer system thereby permits system bus devices, operating at different clock frequencies, to coexist on the system bus without hindering the performance of the faster speed devices.

Computer system with varied data transfer speeds between system

A protocol and system for providing a next read address during an address phase of a write transaction in a data cache unit in a processing unit is disclosed. The processing unit includes the data cache unit and an instruction cache unit both coupled to an address bus and a data bus, respectively. The two buses are further connected to a system memory controller separate from the microprocessor. The protocol and system provide for next read address and a next transaction during the address phase in a current write transaction. The protocol loads a pre-fetched address within a current data transaction and then generates a next line fill address using the pre-fetched address which is concatenated to the current data transaction. The pre-fetched address is used to generate a next line fill address. The line fill address is generated upon determining if a cache read miss has occurred and if so, copying a modified cache line back to the main system memory and then loading the missed cache read line into the internal cache from the system memory controller.

Protocol and system for performing line-fill address during copy-back

A computer system is provided, comprising system memory and a memory controller for controlling access to system memory, a central processing unit electrically connected with the memory controller, and a bus interface unit electrically connected to the memory controller by a system bus and electrically connected to an input/output device by an input/output bus. The bus interface unit includes translation logic for temporarily storing, in response to a predetermined set of operating conditions, data transferred between the system bus and the input/output bus through the bus interface unit. The predetermined set of operating conditions occur when (i) the memory controller on behalf of the central processing unit writes data to the input/output device, or (ii) the memory controller on behalf of the central processing unit initiates a read or write cycle destined for the input/output device acting as a slave on the input/output bus, and the data bus width of the memory controller is greater than a corresponding data bus width of the input/output device.

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Austin, TX, United States of America

Cang Ngoc Tran