Sun Microsystems, Inc.

Edward A Dean

Steven E Golson

John F McDonald

In the system of the present invention, a time critical program operating in a window system environment is implemented. The application program containing time critical procedures is divided functionally into two or more processes. The first process contains all of the CPU time slice sensitive or time critical procedures. This process operates independently of the window system interface and communicates directly with the operating system. The second process implements all procedures which require the user input and output through the window system but not including time critical procedures. This process communicates with and operates through the window system interface. The processes exchange data and synchronize execution through the interprocess communication mechanisms such as shared memory such that the two or more processes operate and appear as a single process to the user while insulating the first process from suspension due to window system operations and blocking procedures.

Method for operating multiple processes using message passing and shared

In the system of the present invention, a specialized form of read-ahead, write-behind buffering is provided which enables the host processing system to provide timely responses to device requests that are emulated by the host processor. Each input/output device request is identified by an address to which the device is purportedly mapped to. This address is translated to an address containing a status word for that particular device being emulated. Each status word contains a byte of information either to be sent to the microprocessor as a response during an I/O read operation request by the microprocessor, or to receive data written by the microprocessor in response to an I/O write operation request, and a plurality of status bits which identify the state of the data contained in the I/O status word. Thus, microprocessor I/O write operations may be quickly performed without the need for immediate response by the host processor and responses for various I/O devices emulated can be precomputed and input to the corresponding I/O status words such that when the microprocessor issues a read request to an input/output device the response may be quickly retrieved and returned back to microprocessor with little or no detected response time degradation.

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Westford, MA, United States of America

Edward A Dean