Honeywell Information Systems Inc.

Honeywell Bull, Inc.

Marion G Porter

Garvin Wesley Patterson

Robert W Norman, Jr

William A Shelly

Charles P Ryan

James L King

Richard T Flynn

Earnest M Monahan

Marvin K Webster

John M Woods

Phillip A Angelle

Edward F Weller, Iii

Joseph Charles Circello

Ronald E Lange

John E Wilhite

Clinton B Eckard

Jaime Calle

David S Edwards

Leonard G Trubisky

Donald V Mills

George M Seminsky

Nicolas S Lemak

Dwaine C Pfeifer

Apparatus is disclosed for incorporation in a central processing unit that permits a testing procedure to be executed on the central processing unit in a manner that simulates the normal operation of the central processing unit. The apparatus includes an auxiliary memory unit, in which the test programs are stored, and an auxiliary processor for controlling the central processing unit when the test procedure is initiated and for preparing the central processing unit for execution of the test procedures. Control apparatus of the central processing unit executes the test program retrieved from the auxiliary memory unit. The auxiliary processor regains control of the central processing unit after the test program has been executed, tests the results of the test procedure and returns control to the central processing unit.

Apparatus and method for testing the operation of a central processing

In a data processing system, there is included a central processing unit (CPU) and a main memory for storing computer words, the CPU including a cache unit. In operation, the CPU requests that a computer word be fetched, the computer word to be fetched being identified by a real address location corresponding to a location where the predetermined computer word is stored in main memory. The CPU request to fetch the computer word is coupled through the cache unit such that the cache unit determines whether the computer word is stored within the cache unit. The cache unit comprises a cache for storing predetermined ones of the compter words. A directory is included for storing partial real address information to a corresponding computer word stored in the cache. A detecting element, operatively connected to the cache and to the directory, determines when a hit occurs without any errors. Control logic, operatively connected to the detecting element, makes available to the CPU the requested computer word from the cache or the main memory when an error is detected as a result of attempting to obtain the computer word from the cache.

Apparatus for forcing a reload from main memory upon cache memory error

Apparatus and method for a supervisor for data processing system capable of utilizing a plurality of operating systems. The supervisor includes apparatus for identifying a condition in the data processing system requiring a different operating system. A reserved memory area associated with the currently active operating system is then addressed and register contents of a central processing unit are stored in the reserved memory area. The reserved memory of the operating system being activated is addressed and causes the address of the reserved memory of the operating system being activated, the data related to permitting the physical memory associated with the operating system being activated, contents of registers safestored in the reserve-memory and, data establishing the decor of the operating system being activated are entered in the central processing unit. The operating system to be activated is then enabled, and execution of permitted instructions by the second operating system is begun. The physical memory locations are determined by a real address through use of a paging mechanism permitting storage of portions of the operating systems in non-contiguous groups of locations while isolating the memory available to each operating system.

Apparatus and method for a data processing unit sharing a plurality of

In a cache memory unit including a cache directory identifying signal groups stored in an associated cache storage unit, apparatus and method are disclosed for searching the cache directory during a second portion of the cache memory cycle when the cache directory is not needed for normal operation, to determine if an invalid signal group is stored in the associated cache storage. When an invalid signal is found in the cache storage, this signal group is rendered unavailable to the data processing unit during the present cache memory cycle without interrupting the normal cache memory operation during succeeding cache memory cycles.

Split-cycle cache system with SCU controlled cache clearing during cache

Apparatus and method for an operating system supervisor in a data

A cache clearing apparatus for a multiprocessor data processing system having a cache unit and a duplicate directory associated with each processor. The duplicate directory, which reflects the contents of the cache directory within its associated cache unit, and the cache directory are connected through a system controller unit. Commands affecting information segments within the main memory are transferred by the system controller unit to each of the duplicate directories to determine if the information segment affected is stored in the cache memory of its associated cache memory. If the information segment is stored therein the duplicate directory issues a clear command through the system controller to clear the information segment from the associated cache unit.

Apparatus for cache clearing

A cache unit includes a cache store organized into a number of levels to provide a fast access to instructions and data words. Directory circuits, associated with the cache store, contain address information identifying those instructions and data words stored in the cache store. The cache unit has at least one instruction register for storing address and level signals for specifying the location of the next instruction to be fetched and transferred to the processing unit. Replacement circuits are included which, during normal operation, assign cache locations sequentially for replacing old information with new information. The cache unit further includes detection apparatus for detecting a conflict condition resulting in an improper assignment. The detection apparatus, upon detecting such a condition, advances the relacement circuits forward for assigning the next sequential group of locations or level inhibiting it from making its normal location assignment. It also inhibits the directory circuits from writing the necessary information therein required for making the location assignment and prevents the information which produced the conflict from being written into cache store when received from memory.

Cache unit information replacement apparatus

A data processing system comprises a data processing unit coupled to a cache unit which couples to a main store. The cache unit includes a cache store organized into a plurality of levels, each for storing blocks of information in the form of data and instructions. The cache unit further includes control apparatus, an instruction buffer for storing instructions received from main store and a transit block buffer comprising a plurality of locations for storing read commands. The control apparatus includes a plurality of groups of bit storage elements corresponding to the number of transit buffer locations. Each group includes at least a pair of instruction fetch indicator elements which are operatively connected to control the writing of first and second blocks of instructions into the instruction buffer. Each time a read command specifying the fetching of instructions of either a first or second block is received from the processing unit, the flag storage element associated with the transit block buffer location into which the read command is loaded is set to a binary ONE state while the corresponding ones of the flag storage elements associated with the other locations storing outstanding read commands specifying instruction fetches are reset to binary ZEROS. This permits only those instructions received from main store in response to that read command to be loaded into a specified section of the instruction buffer for enabling overlaps in processing several commands specifying instruction fetch operations.

Cache apparatus for enabling overlap of instruction fetch operations

A data processing system comprises a data processing unit coupled to a cache unit which couples to a main store. The cache unit includes a cache store organized into a plurality of levels, each for storing blocks of information in the form of data and instructions. The cache unit further includes an instruction buffer having first and second sections for storing instructions received from main store. Each instruction buffer section includes a plurality of word storage locations, each location having a number of bit positions. A predetermined bit position of each location is used to indicate when an instruction word has been written into the location. Control apparatus coupled to each of the buffer sections is operative to reset all of the word locations to binary ZEROS when a command requesting an instruction block from main store is ready to be transferred thereto. It is set to a binary ONE state when an instruction word is loaded into the location. Instruction buffer ready circuits included within the control apparatus are conditioned by the states of the predetermined bit positions of the locations to generate output signals to the processing unit enabling the transfer of requested instruction words to the processing unit as soon as they are received from main store.

Instruction buffer apparatus of a cache unit

A cache unit includes a cache store organized into a number of levels to provide a fast access to instructions and data words. Directory circuits, associated with the cache store, contain address information identifying those instructions and data words stored in the cache store. The cache unit has at least one instruction register for storing address and level signals for specifying the location of the next instruction to be fetched and transferred to the processing unit. Replacement circuits are included which, during normal operation, assign cache locations sequentially for replacing old information with new information. The cache unit further includes apparatus operative in response to a first predetermined type of command specifying the fetching of data words to set an indicator flag to a predetermined state. The apparatus conditions the replacement circuits in response to each subsequent predetermined type of command to bypass storage of the subsequently fetched data words when the indicator flag is in the predetermined state preventing the replacement of extensive numbers of data and instruction words already stored in cache during the execution of the instruction.

Cache unit bypass apparatus

A cache system includes a high speed storage unit organized into a plurality of levels, each including a number of multiword blocks and at least one multiposition address selection switch and address register. The address switch is connected to receive address signals from a plurality of address sources. The system further includes a directory organized into a plurality of levels for storing address information required for accessing blocks from the cache storage unit and timing circuits for defining first and second halves of a cache cycle of operation. Control circuits coupled to the timing circuits generate control signals for controlling the operation of the address selection switch. During the previous cycle, the control circuits condition the address selector switch to select an address which is loaded into the address register during the previous half cycle. This enables either the accessing of instructions from cache or the writing of data into cache during the first half of the next cache cycle. During the first half of the cycle, the address selected by the address switch in response to control signals from the control circuits is clocked into the address register. This permits processor operations, such as the accessing of operand data or the writing of data into cache to be performed during the second half of the same cycle.

Cache arrangement utilizing a split cycle mode of operation

A cache unit couples between a main store and data processing unit. The cache unit includes a cache store organized into a plurality of levels, each for storing blocks of information in the form of data and instructions. The cache unit further includes a write command buffer, a transit block buffer and command queue apparatus coupled to the buffers for controlling the sequencing of commands stored in the buffers. The command queue apparatus includes a plurality of multibit storage locations for storing address and control information. The control information is coded to specify the type of command and the number of words the command contains. The address information is used as a pointer for read out of the command from either the write buffer or transit block buffer simplifying control. Control circuits included within the command queue apparatus in accordance with signals corresponding to the control information and use of the address information control the sequencing of commands so as to maximize the use of the buffer storage capacity.

Command queue apparatus included within a cache unit for facilitating

A data processing system comprises a data processing unit coupled to a cache unit which couples to a main store. The cache unit includes a cache store organized into a plurality of levels, each for storing a number of blocks of information in the form of data and instructions. Directories associated with the cache store contain addresses and level control information for indicating which blocks of information reside in the cache store. The cache unit further includes control apparatus and a transit block buffer comprising a number of sections each having a plurality of locations for storing read commands and transit block addresses associated therewith. A corresponding number of valid bit storage elements are included, each of which is set to a binary ONE state when a read command and the associated transit block address are loaded into a corresponding one of the buffer locations. Comparison circuits, coupled to the transit block buffer, compare the transit block address of each outstanding read command stored in the transit block buffer section with the address of each read command or write command received from the processing unit. When there is a conflict, the comparison circuits generate an output signal which conditions the control apparatus to hold or stop further processing of the command by the cache unit and the operation of the processing unit. Holding lasts until the valid bit storage element of the location storing the outstanding read command is reset to a binary ZERO indicating that execution of the read command is completed.

Cache unit with transit block buffer apparatus

A cache system includes a storage unit organized into a plurality of levels, each including a number of multiword blocks and a corresponding number of address selection switches and address registers. Each address selection switch has a plurality of different positions connected to receive address signals from a plurality of address sources. A decoder circuit generates output signals for controlling the operation of the address selection switches. In response to previously defined level signals, the decoder circuit conditions a specified one of the number of switches to switch from a first position to a second position. An address specifying the location into which memory data is to be written is clocked into one address register while the address specifying the location from which an instruction is to be fetched is clocked into the remaining address registers. A comparator circuit compares signals indicating the level into which memory data is to be written with signals indicating the level from which a next instruction is to be fetched. The comparator circuit generates signals which cause the delay of instruction access when there is a conflict between writing memory data and accessing instructions.

Cache arrangement for performing simultaneous read/write operations

An input/output processing system includes an input/output processing unit and a read only memory (ROM) and a read/write memory. The ROM is coded to include instructions of a number of control routines. The read/write memory includes locations for storing instructions and data. The processing unit includes a plurality of registers for storing information used in developing addresses for accessing each memory. It further includes a control register for storing information for controlling accesses to the memories and a steering register which operatively couples to the control register and stores information designating which one of the memories is to be accessed. The processing unit is conditioned to exclusively OR the information in the control register with the information contained in one of the plurality of registers. By logically combining the contents of the control register and contents of another register during each address development operation, the processing unit is able to switch between the two memories as desired. When it is desired to start or stop accessing instructions from ROM, the processing unit is conditioned to perform an OR or AND operation respectively upon the contents of the control register with the contents of the other register and place the result in the control register.

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Phoenix, AZ, United States of America

Marion G Porter