Browse Prior Art Database

Adaptive Mailbox Timer

IP.com Disclosure Number: IPCOM000122044D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Irwin, JW: AUTHOR

Abstract

A Micro Channel* adapter starts a timer for selected mailbox operations that are passed to controllers for execution. The timer is set to an initial negative value appropriate to the operation in progress and all non-zero timers are incremented by the idle task at each tick of a timer. If the counter overflows, an error is posted. This is the existing art. In order to make the timer more responsive to the machine environment, a level of adaptation has been introduced as follows: 1. The timer increment is suppressed if any status is queued up to be presented to the Device Driver. Thus, if the host machine cannot keep up because of excessive load or is stopped for debugging, no spurious timer errors are posted, 2.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 63% of the total text.

Adaptive Mailbox Timer

      A Micro Channel* adapter starts a timer for selected
mailbox operations that are passed to controllers for execution. The
timer is set to an initial negative value appropriate to the
operation in progress and all non-zero timers are incremented by the
idle task at each tick of a timer.  If the counter overflows, an
error is posted.  This is the existing art.
In order to make the timer more responsive to the machine
environment, a level of adaptation has been introduced as follows:
 1.  The timer increment is suppressed if any status is queued up to
be presented to the Device Driver.  Thus, if the host machine cannot
keep up because of excessive load or is stopped for debugging, no
spurious timer errors are posted,
 2.  The timer is stopped completely after certain commands of
indefinite duration are safely started and is restarted with an
appropriate count when the controller signals that the operation has
reached a predictable phase. Thus, the timer covers the predictable
portions of the operation.
 3.  If the adapter receives an EXTEND request from the controller,
all timers for mailboxes assigned to that device are extended a set
time by subtracting a constant from the timer count.  Thus, extended
error recovery action does not result in timer errors.
 4.  When the controller returns ending status, the timer is adjusted
to a very short interval regardless of the existing count.  This
short interval then covers the action of t...