Browse Prior Art Database

POS Register Definition Architected for Up to 8 Simms

IP.com Disclosure Number: IPCOM000099960D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Hanna, JT: AUTHOR [+3]

Abstract

Disclosed is a method to allow software to enable and configure the interface for up to 8 Single In-line Memory Modules (SIMMs) while using just two I/O port addresses. This method is compatible with the IBM Personal System/2* Programmable Option Select (POS).

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This is the abbreviated version, containing approximately 61% of the total text.

POS Register Definition Architected for Up to 8 Simms

       Disclosed is a method to allow software to enable and
configure the interface for up to 8 Single In-line Memory Modules
(SIMMs) while using just two I/O port addresses. This method is
compatible with the IBM Personal System/2* Programmable Option Select
(POS).

      The IBM Personal System/2 computers contain a block of I/O
addresses used to communicate configuration information from the
system planar and the installed I/O features.  This register block is
contained within the POS definition.  When the planar or an I/O
feature has been selected, it responds to I/O references within the
POS range.  Only one device at a time is selected for POS mode.

      In a system with a variable number of memory SIMMs, it is
necessary to communicate information about the SIMMs between the
memory controller and the system processor. Specifically, the
power-on- self-test software (POST) needs to read the 4
identification bits for each SIMM to determine the size and access
speed of planar memory.  POST then performs a planar memory test and,
based on the results of the memory test, writes a memory enable
pattern to the memory controller for each SIMM.  This four-bit memory
enable pattern is used to disable any bad memory banks that were
detected during the POST memory test.  Since the memory controller
communication only takes place during setup, it is desirable to
incorporate the communication registers in th...