Browse Prior Art Database

Multi-Configurablity of TCW/TAG Memory

IP.com Disclosure Number: IPCOM000099638D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 31K

Publishing Venue

IBM

Related People

Arimilli, RK: AUTHOR [+4]

Abstract

The Tag word used in the Third Party DMA Controller in the I/O Channel Controller (IOCC) chip which generates the MICRO CHANNEL*, is 8 bytes wide and the Translation Control Word (TCW) used in the First Party DMA Controller is 4 bytes wide. The Tag/TCW words are contained in 512K bytes of dynamic memory external to the IOCC chip that contains the Third and First Party DMA Controllers. The tags are contained in 32K bytes and the TCWs are in the remaining 480K bytes.

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This is the abbreviated version, containing approximately 100% of the total text.

Multi-Configurablity of TCW/TAG Memory

       The Tag word used in the Third Party DMA Controller in
the I/O Channel Controller (IOCC) chip which generates the MICRO
CHANNEL*, is 8 bytes wide and the Translation Control Word (TCW) used
in the First Party DMA Controller is 4 bytes wide.  The Tag/TCW words
are contained in 512K bytes of dynamic memory external to the IOCC
chip that contains the Third and First Party DMA Controllers.  The
tags are contained in 32K bytes and the TCWs are in the remaining
480K bytes.

      The time to access the external dynamic memory is 200 ns.  The
interface between the IOCC chip and the external memory can be 2 or 4
bytes.  If the interface is 2 bytes, the Tag access requires 4 cycles
of 2 bytes each and the TCW access requires 2 cycles.  A 4-byte
interface would require 2 and 1 cycle for the Tag and TCW,
respectively.

      A three-bit field is provided inside the IOCC chip which
determines the width of the above interface.  The 2-byte interface
has a slower access time but is cheaper. The 4-byte interface is
faster at a greater cost.  The bits provided in the IOCC enables the
design to choose either interface, depending on the system
environment.
* Trademark of IBM Corp.