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Automatic Request Response Control Block DMA for High Performance IOP

IP.com Disclosure Number: IPCOM000102130D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 4 page(s) / 156K

Publishing Venue

IBM

Related People

Huss, FL: AUTHOR [+4]

Abstract

Bus Transport Mechanism (BTM) architected data transfers require input/output processor (IOP) microcode management of the BTM data structures. The required microcode management of the BTM data structures increases IOP microprocessor utilization.

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Automatic Request Response Control Block DMA for High Performance IOP

       Bus Transport Mechanism (BTM) architected data transfers
require input/output processor (IOP) microcode management of the BTM
data structures.  The required microcode management of the BTM data
structures increases IOP microprocessor utilization.

      The performance of the IOP is improved, and the IOP
microprocessor utilization is reduced by imbedding the Automatic
Request Response Control Block (RRCB) DMA control logic into the IOP
Bus Adapter.

      The features of the Automatic RRCB DMA are:
      -  The Automatic RRCB DMA decreases IOP microprocessor
utilization by reducing microcode management of BTM data structures.
 -  The Automatic RRCB DMA requires no modifications to existing BTM
data structures.
      -  Overall performance of the IOP is increased due to the
reduction in required microcode intervention.

      The BTM provides a transport mechanism to be used by the Inter-
Process Communication Facility (IPCF) to transport data across the
I/O Bus.

      The BTM defines the set of bus unit messages and data
structures for moving data across the I/O Bus between requestors and
servers that reside in different processors on the bus.  A processor
may be either the Bus Control Unit (BCU) or another bus unit (IOBU)
on the I/O Bus as defined in the main processor's I/O Architecture.
Bus error recovery procedures are also defined.

      The BTM is unaware of the format and content of any
device-specific or I/O processor specific data that is moved between
the requestor and the server.  The BTM provides communication
capability between bus units if one has master DMA capability and the
other has slave DMA capability.

      The BTMs in two different I/O processors communicate on the I/O
Bus via Bus Unit Messages and RRCBs.

      A Bus Unit Message initiates all communications between bus
units on the I/O Bus.  The Bus Unit Message provides the basic
information for further communication that may require using DMA
facilities.  Some operations require only a Bus Unit Message.

      The RRCB is the control block that is used by the BTM in the
requestor processor and the BTM in the server processor to control
the movement of data between the processors.  The RRCB is utilized
for the physical DMA process between the server's and requestor's
storage.

      BTM OP START BUS UNIT MESSAGE:  The Operation Start Bus Unit
Message is used to alert the server BTM that there is an RRCB that
requires service.  The OPSTART Bus Unit Message contains the
Connection ID (CID) that identifies the connection between a
requestor process and the server process.

      "Automatic RRCB DMA" is implemented using a set of registers in
the IOP Bus Adapter which are initialized by the IOP microcode prior
to the receipt of OPSTART Bus Unit Messages.  The IOP Bus Adapter
contains three sets of registers, one for each CID...