Browse Prior Art Database

Low-Power Overlapping Refresh Mechanism for Two-Sided DRAM SIMMs

IP.com Disclosure Number: IPCOM000120611D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Eng, RC: AUTHOR [+3]

Abstract

This article describes a technique which enables a two-sided dynamic RAM (DRAM) single in-line memory module (SIMM) to be refreshed which minimizes peak current requirements during the refresh cycle without separate refresh cycles for each side of SIMM.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 57% of the total text.

Low-Power Overlapping Refresh Mechanism for Two-Sided DRAM SIMMs

      This article describes a technique which enables a
two-sided dynamic RAM (DRAM) single in-line memory module (SIMM) to
be refreshed which minimizes peak current requirements during the
refresh cycle without separate refresh cycles for each side of SIMM.

      DRAM is a typical storage medium for computer systems. The
interface to DRAM is provided through  Address lines, Data line(s), a
Row Address Strobe (RAS), a Column Address Strobe (CAS), and Write
Enable (WE) line.  This type of memory requires a periodic refresh
cycle to maintain the storage of valid data.  The refresh cycle for a
DRAM typically consists of a valid address and a pulse of the RAS to
the DRAM device.

      The SIMM is circuit card containing multiple DRAM modules and
an interface to a system memory control circuit. This interface
appears to the system circuitry as a single DRAM with multiple data
bits.  A typical data width is 36 bits of data.  The SIMM package can
also be a two-sided circuit card with separate RAS signals to control
each 36-bit block of data.  The RAS signal for side one of the SIMM
shall be named RAS-A.  The RAS signal for side two of the SIMM shall
be named RAS-B.

      The SIMM electrical specification requires that the RAS-A and
RAS-B signals cannot be active at the same time in order to limit the
current draw of the SIMM during refresh. To refresh the two-sided
SIMM requires a separate...