Browse Prior Art Database

Non-refresh Dynamic Random Access Memory and Cache Memory

IP.com Disclosure Number: IPCOM000109140D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Related People

Montoye, RK: AUTHOR

Abstract

Described is a technique applied to dynamic random access memory (DRAM) and cache memory devices, as used in computer systems, which require no refresh, timers or stand-by power. The technique is also fail-safe against alpha particles.

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This is the abbreviated version, containing approximately 99% of the total text.

Non-refresh Dynamic Random Access Memory and Cache Memory

      Described is a technique applied to dynamic random access
memory (DRAM) and cache memory devices, as used in computer systems,
which require no refresh, timers or stand-by power.  The technique is
also fail-safe against alpha particles.

      Typically, DRAMs are four to six times the density of static
RAMs.  However, the DRAMs have several weaknesses, such as: a) the
charge eventually leaks away; b) alpha particles leak from the cell
immediately; and c) the cycle time is two times the access time.

      In a cache memory where no modification of data in memory is
performed, a DRAM can be successfully used without refreshing as
follows:
       .  Choose a large bit line, such as a 512 bit line.
       .  Count the number of one's and place this count in a static
RAM directory.
       .  Check and refresh the line on accessing to the line.
         Reload the line if a fail check should occur.
       .  Use the large bit line to overcome the lack of bit accesses
on consecutive accesses.

      The technique is viable since DRAM bits will only lose their
charge, including alpha particles.  Since all data in the cache is
backed up in main memory, data is never lost; therefore, this virtual
refresh caused by non-access to a line until it fails is done only
when the charge on the cell actually leaks away and is then
requested.

      Disclosed anonymously....