Honeywell Information Systems Inc.

Honeywell Bull, Inc.

Daniel A Boudreau

Edward R Salas

James M Sandini

Chester M Nibby, Jr

Robert B Johnson

Edwin P Fisher

Richard C Zelley

A method for determining the maximum amount of physical memory present in a data processing system that can be configured to have one or more memory modules where the memory modules may be one of several types having different amounts of memory locations. By having signals indicating the presence of a memory module and the module type directly available with minimal intervening logic, a diagnostic process can accurately determine the amount of memory present in the system and reduce the possibility of a failed memory module going undetected. A method is also descibed using these memory module present and module type signals for detecting an attempt by either the central processor or an input/output controller to access a memory location that is not physically present within the data processing system.

Technique for determining maximum physical memory present in a system

A data processing system includes an asynchronous parallel multiport volatile main memory system accessible directly by any one of M number of central processing units or by I/O controllers connected in common to any one of N number of system buses. Priority resolver circuits award access to main memory on a predetermined priority basis. Each port includes address, data in, data out, timing and control circuits which operatively couple to the priority resolver circuits. The circuits of each port and the central processing unit or system bus I/O controllers associated therewith operate independently of each other in an asynchronous manner to access and store data and to report errors.

Asynchronous multiport parallel access memory system for use in a single

A data processing system including a dual ported main memory that can be accessed by I/O controllers via a common bus or directly by the central processing unit. The main memory is comprised of a volatile RAM array that requires periodic refreshing to prevent loss of information. Access to the main memory is controlled by a priority resolver that awards access to the main memory on the basis of predetermined priority levels assigned to CPU, I/O and refresh requests. The priority resolver produces an early signal that is usable to initiate a memory cycle before the final winner of the main memory is determined. The logic path of the lowest priority requester is the shortest path thus allowing the lowest priority requester to initiate a memory cycle in the shortest amount of time even though another requester may ultimately win use of the memory. The priority resolver also provides for the early resetting of access requests so that subsequent requests can be made with minimum delay.

Priority resolver with lowest priority level having shortest logic path

A data processing system having a plurality of units includes a shareable unit which is shareable between two or more of the other units. Lock apparatus is provided in the shareable unit to allow a first unit to lock the shareable unit so that no other unit attempting to lock the shareable unit will be permitted access to the shareable unit. The lock apparatus includes means that permit two units desiring to lock the shareable unit to make simultaneously asynchronous requests to lock the shareable unit. The lock apparatus further includes means to permit the unit which has locked the shareable unit to unlock the shareable unit so that it becomes available for a subsequent lock by a unit. The lock apparatus also includes means to allow the shared unit to be accessed by other units not attempting to lock the shareable unit even when the shareable unit is locked.

Lockout operation among asynchronous accessers of a shared computer

A single computer board data processing system includes a multiport memory system which is accessible by I/O controllers through a system bus I/O memory port or directly by the system's central processing unit (CPU) via a CPU memory port. The logic and control circuits of the memory ports and CPU are included within the computer main board while memory modules/pacs are contained on one or more memory daughter boards which plug into memory input/output connectors contained on the main board. The port address and data paths connect in common to the memory connectors for transmitting and receiving memory addresses and data between the memory modules and the CPU and I/O ports. At least one register connects between the CPU and to common address path. When the CPU is placed in a diagnostic mode of operation, this register together with existing data registers are conditioned to store signals representative of the address and data being transmitted to the memory modules enabling the CPU to diagnose whether the main board or portions thereof has failed without requiring any testing of the memory modules.

Memory architecture for facilitating optimum replaceable unit (ORU)

In a data processing system, a bus is provided for the transfer of information between units coupled to the bus. The units are coupled in a priority arrangement which is distributed thereby providing priority logic in each of the units and allowing bus transfer cycles to be generated in an asynchronous manner. Priority is normally granted on the basis of physical position on the bus, highest priority being given to the first unit on the bus and lowest priority being given to the last unit on the bus. Each of the units includes priority logic which includes logic elements for requesting a bus cycle, such request being granted if no other higher priority unit has also requested a bus cycle. The request for and an indication of the grant of the bus cycle are stored in each unit so requesting and being granted the bus cycle respectively, only one such unit being capable of having the grant of a bus cycle at any given time, whereas any number of such units may have its request pending at any particular time. A modification to the priority logic allows a lowest priority unit to be physically positioned at other than the last unit position on the common bus.

Distributed priority network logic for allowing a low priority unit to

A memory system includes at least one or more memory module boards identical in construction and a single computer board containing the control circuits for controlling memory operations. Each board plugs into the main board and includes a memory section having a number of rows of memory chips and an identification section containing circuits for generating signals indicating the board density and the type of memory parts used in constructing the board's memory section. The main board control circuits include a number of decoder circuits which couple to the identification and to the memory section of each memory module board. The decoder circuits receive different address bit combinations of a predetermined multibit address portion of each memory request address. In response to signals generated by the identification sections of the installed memory boards, the decoder circuits are selectively enabled to decode those bit combinations of the address portion specified by the sections for enabling successive addressing of all of the blocks of location within the system.

Memory identification apparatus and method

An auto address development logic that, when provided a starting address, is used to develop consecutive addresses as multiple words of information are presented, one word at a time, during multiple consecutive information transfer cycles. The logic retains for use a current address while simultaneously developing the next address so that the next address will be immediately available as the current address at the beginning of the next information transfer cycle. The auto address development logic is used in a system analyzer connected to a data processing system having a common bus over which the CPU, during a first bus cycle, provides a starting address and requests that the memory fetch multiple words of information which are transferred to the CPU, during multiple subsequent responding bus cycles.

Data processing system auto address development logic for multiword fetch

A common bus utilization detection logic that is used when a particular device connected to a common bus has been granted access to the common bus wherein bus access is granted on a priority basis. By positioning the bus utilization logic in priority positions on the common bus adjacent to the particular device whose bus use is to be detected, the bus utilization detection logic can determine when the common bus has been awarded to the particular device even though there may have been other devices simultaneously requesting access to the common bus. The bus utilization detection logic is used in a system analyzer connected to a data processing system having a common bus and permits the analyzer to be connected in the same manner as other devices are connected to the common bus. Also disclosed is a software analyzer and a data processing system having an asynchronous bus on which multiple words of data can be read from memory in response to a read request providing a starting memory address.

Data processing system common bus utilization detection logic

A data processing system including a dual ported main memory that can be accessed by I/O controllers via a common bus or directly by the central processing unit. The main memory is comprised of a volatile RAM array that requires periodic refreshing to prevent loss of information. Access to the main memory is controlled by a priority resolver that awards access to the main memory on the basis of predetermined priority levels assigned to CPU, I/O and refresh requests. The priority resolver produces an early signal that is usable to initiate a memory cycle before the final winner of the main memory is determined. The logic path of the lowest priority requester is the shortest path thus allowing the lowest priority requester to initiate a memory cycle in the shortest amount of time even though another requester may ultimately win use of the memory. The priority resolver also provides for the early resetting of access requests so that subsequent requests can be made with minimum delay. Logic is provided that allows the predetermined priority levels to be adjusted dynamically as a function of system conditions.

Priority resolver having dynamically adjustable priority levels

Apparatus and method for performing a logical not function in a multi-compare environment is disclosed. By performing two equivalence compares of a measured variable against selectable target values and using the result of the equivalence compares to selectivity set or reset a bistable element, the need for inverting and multiplexing the output of a comparator that is otherwise required when performing a NOT equivalence function in a single-compare environment is eliminated. The not function logic is used in a system analyzer connected to a data processing system and is used to selectively enable the tracing of software execution as a function of whether or not a variable is a predefined value.

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Billerica, MA, United States of America

Daniel A Boudreau