Browse Prior Art Database

Extended Micro Channel for Realtime Multimedia Applications

IP.com Disclosure Number: IPCOM000109959D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 3 page(s) / 118K

Publishing Venue

IBM

Related People

Lee, TC: AUTHOR [+2]

Abstract

Disclosed is an extended design to MICRO CHANNEL* that provides better services to adapters with realtime constraints. A new realtime priority class is added in this design with a few newly added signals, RB0, RB1, RARB/-RGRANT and -RPREEMPT. The realtime arbitration and realtime data transfer are embedded in the non-realtime arbitration cycle. The channel bandwidth is effectively partitioned between the two classes such that realtime requests will not get much interference from non-realtime ones, and the channel will not be monopolized by realtime adapters.

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Extended Micro Channel for Realtime Multimedia Applications

       Disclosed is an extended design to MICRO CHANNEL* that
provides better services to adapters with realtime constraints.  A
new realtime priority class is added in this design with a few newly
added signals, RB0, RB1, RARB/-RGRANT and -RPREEMPT.  The realtime
arbitration and realtime data transfer are embedded in the
non-realtime arbitration cycle.  The channel bandwidth is effectively
partitioned between the two classes such that realtime requests will
not get much interference from non-realtime ones, and the channel
will not be monopolized by realtime adapters.

      The realtime arbitration scheme is described below.  Suppose
that at time a a realtime device A wants to request the channel.
Device A activates the -RPREEMPT signal to request a realtime
arbitration cycle.  If the channel is idle at the time, the central
arbitration control point first enters the non-realtime arbitration
cycle (by raising ARB/-GRANT) and then immediately enter the realtime
arbitra tion cycle (by raising RARB/-RGRANT).  The channel is granted
to A if no others are competing.  If the channel is occupied by a
non-realtime device B, the central arbitration control point raises
ARB/-GRANT signal to preempt B. B then releases the channel within
7.8 microseconds.  The central arbitration control point enters the
non-realtime arbitration cycle and then the realtime arbitration
cycle.  If the channel is held by a realtime device C, device C has
to release the channel within Trealtime microseconds, where Trealtime
is a predefined time interval.  The central arbitration control point
then enters the realtime arbitration cycle.  The figure illustrates
the case when a realtime device competes against a non-realtime
device.  The channel enters a realtime arbitration cycle at time b.
Because the realtime arbitration is embedded in the non-realtime
arbitration cycle, a non-realtime arbitration cycle also starts at b.
The non-realtime arbitration cycle ends at d, after  the realtime
operation completes.  The channel is then granted to the competing
non-realtime device.

      When multiple realtime devices are competing for the channel,
fairness policy in current MICRO CHANNEL is used.  This provides fair
channel sharing among realtime devices.  However, to remove the
potential monopolization of the channel by realtime devices, after k
realtime cycles (tracked by a counter) or k Trealtime microseco...