Browse Prior Art Database

Novel Memory Card

IP.com Disclosure Number: IPCOM000113953D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 140K

Publishing Venue

IBM

Related People

Coteus, PW: AUTHOR [+2]

Abstract

The performance and to a large extent the cost of modern day portable computers is a function of the size of DRAM memory. Thus, it is traditional that this memory be user upgradeable. The most popular form of pluggable memory, the DRAM SIMM, is a poor match to the compact size, light weight, and 16 bit data busses of modern portable computers. A new memory card is proposed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 47% of the total text.

Novel Memory Card

      The performance and to a large extent the cost of modern day
portable computers is a function of the size of DRAM memory.  Thus,
it is traditional that this memory be user upgradeable.  The most
popular form of pluggable memory, the DRAM SIMM, is a poor match to
the compact size, light weight, and 16 bit data busses of modern
portable computers.  A new memory card is proposed.

      The solution to this problem is to make a new memory card,
shown below.  The card provides 8,9,16, or 18 bits of data.  If built
of flex, the card may be bent into new geometries for better
packaging efficiency.  Because the card is based on a two piece
connector, it is possible to stack cards.
Side views of various memory card configurations.  Dimensions in
inches.
Sizes are for 51 pin connector, 4 Mb DRAMs.
 o   (a) Side view of Fig. 1.
 o   (b) Stacking version of (a).
 o   (c) Bent wing version of (a) for improved cooling.
 o   (d) Stacking version of (c).
 o   (e) Triangulated version of (a) for minimal footprint.
 o  (f) Increased capacity version of (a), folded for minimal
footprint.
 o   (g) Stacking version of (f).

      Fig. 1 shows an example of the proposed memory card.  One half
of a two piece connecter is mounted on the center of one side of a
thin, flexible circuit card.  In this example there are 51 leads,
containing 18 data lines, 12 address lines, 4 Row Address lines
(RAS), 4 Column Address lines (CAS), one Write Enable line (WE), 4
Presence Detect line (PD), 4 power lines, and 4 ground lines.  If
necessary PD pins may be traded for power and/or ground pins.  These
lead assignments allow both a single byte (8 or 9 bits) or double
byte (16 or 18 bit) accesses, from up to 4 sets of DRAMs, and is thus
compatible for processors designed for the SIMM memory cards and/or
88 pin DRAM cards.  Also on the card are four memory chips, providing
either 8 or 9 data bits each, which are placed on either side of the
connector.  Shown are 4 Megabit (Mb) DRAMs in Thin Small Outline
Plastic packages (TSOPs) containing either 8 or 9 data lines.  The
less expensive 8 bit chips are for systems without parity.  The 12
data lines on the memory card enable the use of the larger 16 Mb
DRAMs for a larger capacity memory card.  Other pinned or surface
mount modules may be used, but the smaller and thinner the better.
There are capacitors for decoupling of the power planes and resistors
for asserting a connection between a presence detect pin and a stable
voltage source.

      The DRAM's modules are available in a reverse lead pattern,
such that DRAMs mounted on either side of a circuit card can share a
set of contacts.  Use of both forward and reverse leaded packages can
greatly simplify the wiring of the circuit card, while introducing a
symmetry to the multidrop nets that can improve electrical
performance.  The locations of the regular and reverse leaded DRAMs
are shown in Fig. 1.  With t...