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Time Stamping

IP.com Disclosure Number: IPCOM000078294D
Original Publication Date: 1972-Dec-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Fichtner, DR: AUTHOR [+2]

Abstract

Accurate time stamping is a requirement for measuring the performance of data-processing machines and programs. An especially important time is the time of the beginning of actual receipt of a message as seen by the user, such as the start of typing by an IBM 2741 terminal of a message from an IBM System/360-370. A technique which calculates the start time by subtracting a character time for each character in the message from the end time of the message is inaccurate, when the message includes idle characters.

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Time Stamping

Accurate time stamping is a requirement for measuring the performance of data-processing machines and programs. An especially important time is the time of the beginning of actual receipt of a message as seen by the user, such as the start of typing by an IBM 2741 terminal of a message from an IBM System/360-370. A technique which calculates the start time by subtracting a character time for each character in the message from the end time of the message is inaccurate, when the message includes idle characters.

The objective in time stamping the "start of receive' is to determine the actual start of typing that the user would see. To do this, a program-controlled I/O interrupt (PCI) technique is used.

A PCI causes an I/O interrupt during the execution of an I/O operation. Basically, the interrupt handling routine takes the value of the CLOCK at that instant and adjusts the value depending on the type of machine. The time of the interrupt may depend upon the model of CPU being used, e.g. a System/370 Model 155 causes a PCI at the fetch time of the CCW (Channel Command Word), while a System/360 Model 50 causes a PCI at the beginning of data transfer.

The following is a list of CCW's used in the receiving of a message. In this technique, the first two CCW's will record the accurate start time of the message received regardless of the CPU used. REC1 CCW INHIBIT,INPUT1,DC+SLI+PCI,1 REC15 CCW INHIBIT,INPUT1+1.DC+SLI+PCI,131 REC2 CCW INHIBIT,INPUT2,DC+SLI+P...