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Programmable Memory Address Decoder for Personal Computer Systems

IP.com Disclosure Number: IPCOM000120822D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 113K

Publishing Venue

IBM

Related People

Alvarez, R: AUTHOR [+6]

Abstract

Described is a programmable address decoder for personal computer systems which utilize a Micro Channel* (MC). The concept provides a means whereby an adapter memory unit can reside anywhere within a four gigabyte system memory address space. It allows the memory space to be defined dynamically, depending on the amount of memory available and the system requirements.

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Programmable Memory Address Decoder for Personal Computer Systems

      Described is a programmable address decoder for personal
computer systems which utilize a Micro Channel* (MC).  The concept
provides a means whereby an adapter memory unit can reside anywhere
within a four gigabyte system memory address space.  It allows the
memory space to be defined dynamically, depending on the amount of
memory available and the system requirements.

      There are five memory address registers (MARs) used to assign
and access adapter memory space.  Three of the five MARs are used to
compare MC addresses with assigned addresses and two of the five MARs
are used to define the range that the memory is to encompass, such as
defining a memory 8K bytes wide or 16M bytes wide and translate
system memory addresses to adapter memory addresses.  Three memory
address registers (MSAR0, MSAR1 and MSAR2) are used to locate the
starting address of the system memory that is to reside on an adapter
card.  The three MSARs, as shown in Fig. 1, are loaded with the MC
address that the adapter memory is required to answer to.

      Two memory base registers (MSBRO and MSBR1), as shown in Fig.
2, contain both the translated location of the adapter memory and the
range that the memory will cover.  Together, the registers allow the
adapter memory range to be placed virtually anywhere within a 16M
byte adapter memory address space.  The size of the memory is limited
by the space availabl...