Browse Prior Art Database

Delayed/Distributed Dynamic RAM Refresh

IP.com Disclosure Number: IPCOM000120587D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Drerup, BC: AUTHOR [+2]

Abstract

This article describes a technique of adding "delays" to refresh adapter cards in a personal computer (PC) system with dynamic RAMs (DRAMs) to minimize power demand and current surge from the power supply.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 74% of the total text.

Delayed/Distributed Dynamic RAM Refresh

      This article describes a technique of adding "delays" to
refresh adapter cards in a personal computer (PC) system with dynamic
RAMs (DRAMs) to minimize power demand and current surge from the
power supply.

      For a DRAM to properly maintain its contents, it must be
periodically refreshed.  Typically, when a bank of memory is
refreshed, every memory chip is enabled.  This results in much larger
power consumption during a refresh cycle than during normal
operations (data access or idle).  Many PCs perform refresh cycles on
the bus.  This allows the simultaneous refresh of memory on all
adapter cards.

      Within a PC system, if the quantity of memory being refreshed
at once is very large, the power supply may be unable to supply
enough current.  Also, the sudden power surge may cause voltage
spikes throughout the system, which may interfere with proper
operation of the system's circuitry.  If several add-in cards are
plugged into the system and each card contains a large amount of
memory, the power surges described above will occur if all the memory
is refreshed simultaneously.

      All the cards in the system should not refresh their memory
simultaneously.  Instead, each card should delay refresh by a
different amount of time.  The delay can be introduced by using a
timer between the bus refresh signal and the local refresh signal, as
shown in block diagram in the drawing.  To provide unique amoun...