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Multiple Command Time-Outs for Multi-Tasking Computer Systems

IP.com Disclosure Number: IPCOM000115425D
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 93K

Publishing Venue

IBM

Related People

McNeill, AB: AUTHOR [+3]

Abstract

Described is a hardware/firmware implementation that provides multiple command time-out checking for multi-tasking computer systems. A method is described that handles time-outs on a multi-tasking system, or subsystem, so as to allow a short constant time period on the interrupt level.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Multiple Command Time-Outs for Multi-Tasking Computer Systems

      Described is a hardware/firmware implementation that provides
multiple command time-out checking for multi-tasking computer
systems.  A method is described that handles time-outs on a
multi-tasking system, or subsystem, so as to allow a short constant
time period on the interrupt level.

      Typically, in multi-tasking computer systems and subsystems,
hundreds of commands or tasks can be active at any given moment.
Keeping a time-out value for each command or task can involve
additional system processing overhead.    Each command requires space
to record a unique time stamp.  Space for storage becomes a variable
in the design with many overlapped commands active at a given time.
Host systems usually require large time-out periods for each command,
requiring large amounts of storage.  As a result, a method was needed
to keep the time-outs on commands or tasks running with minimum
overhead and maximum simplicity so as to allow for large time-out
periods.  For example, some tape drives require several hours to
complete a single tape erase command.

      The concept described herein provides a simple low storage
time-out method which a gate array can incorporate.  The multiple
command time-out implementation allows for a short constant time
period on the interrupt level and a user friendly system interface.
A time-out value per command is passed from the host to the adapter
using seventeen bits of information within each element.  Sixteen
bits of information are in seconds or minutes.  Accuracy is
maintained at plus or minus one second up to a value of 65,535
seconds, or 18.2 hours.  Accuracy is also maintained at plus or minus
one second up to a time value of 65,535 minutes, or 1,092.25 hours.
In this way, the host can maintain an accuracy for short or long
durations and has a user friendly interface to change to a longer
period of time.

      The Figure shows a block diagram of how the timer handler
controls the multiple command time-outs.  First, the seventeen bits
of information from the host are saved in its original form for
reducing the transformation time, as...