Browse Prior Art Database

Control Frame Multiplexing On Serial I/O Channels

IP.com Disclosure Number: IPCOM000099927D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Related People

deVeer, JA: AUTHOR

Abstract

Disclosed is a method of removing the effects of cable length and control-unit overhead from I/O channel throughput by providing the channel with the means of multi-tasking between multiple concurrent I/O operations. I/O channels, thus equipped, have the potential for significantly higher I/O throughput and improved response times.

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This is the abbreviated version, containing approximately 52% of the total text.

Control Frame Multiplexing On Serial I/O Channels

       Disclosed is a method of removing the effects of cable
length and control-unit overhead from I/O channel throughput by
providing the channel with the means of multi-tasking between
multiple concurrent I/O operations.  I/O channels, thus equipped,
have the potential for significantly higher I/O throughput and
improved response times.

      Conventional IBM System/370 I/O channels operate on a single
I/O operation at a time, remaining in correspondence with a control
unit for complex sequences of command and control exchanges and data
transfers.  The result is that the I/O channel is largely idle during
control sequences because it is 'busy' for all practical purposes
while the control-unit is performing its part of the sequence; and
the channel incurs even longer waits as cable distances are
increased.  In the subject disclosure, by supplying the I/O channel
with intermediate parameter storage, the channel is able to save the
state of a process for which it has just sent a control frame, and
task switch to another I/O operation which is ready for channel
service.  In this way the channel can have multiple I/O operations in
progress concurrently, using its resource only when an operation
requires more information from, or the participation of, the channel.

      Tasks for which a control frame has just been sent are placed
on a wait queue, maintained in the channel's parameter storage.  As
return frames are received by the channel, the tasks to which they
pertain are moved...