Browse Prior Art Database

Highly Precise System Timer Making Use of Slow Arrays

IP.com Disclosure Number: IPCOM000118996D
Original Publication Date: 1997-Oct-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 83K

Publishing Venue

IBM

Related People

Gartner, U: AUTHOR [+4]

Abstract

As multi-processor systems become faster and faster, it is necessary to provide more precise timers, which are used to distinguish different actions. For reasons of chip space, the different timer values are stored in one common array. Therefore, an immediate read- or write-access is not possible. A central facility provides pulses, which update and synchronize all timer values of all the processors in the system. In order to allow for a simplified signal distribution, these pulses do have a frequency that is lower than the system's clock frequency. In order to be able to precisely distinguish between different actions, a subdivision of the time intervals between two update pulses is required. This is achieved by means of an interpolation counter, which is driven by the system's clock frequency.

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Highly Precise System Timer Making Use of Slow Arrays

      As multi-processor systems become faster and faster, it is
necessary to provide more precise timers, which are used to
distinguish different actions.  For reasons of chip space, the
different timer values  are stored in one common array.  Therefore,
an immediate read- or write-access is not possible.  A central
facility provides pulses, which  update and synchronize all timer
values of all the processors in the system.  In order to allow for a
simplified signal distribution, these  pulses do have a frequency
that is lower than the system's clock frequency.  In order to be able
to precisely distinguish between different actions, a subdivision of
the time intervals between two update  pulses is required.  This is
achieved by means of an interpolation counter, which is driven by the
system's clock frequency.  Because a common array holding several
different timer values is used, a more complex method than simply
resetting this interpolation counter is needed.  The solution to this
problem is described in the following:

      In order to improve the resolution of the system timers, a
clock frequency driven timer is used which continues counting between
two of said central update pulses.  Whenever a value of the timer
array is read, the instantaneous value of the timer is added to the
content of the timer array.  Thus, it is possible to improve the
resolution of the array timers by means of this interpolation timer.
In our example, a four-bit counter allows for an improvement in the
resolution by a factor of 16.  This implies that even in case the
timer accesses of different processors are only one clock cycle
apart, they can be distinguished.  Without the interpolation counter
(also referred...