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From: mir@opera.chorus.fr (Adam Mirowski)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Paged mode SIMMS, what are they?
Message-ID: <7748@chorus.fr>
Date: 5 Feb 91 16:16:46 GMT
References: <1991Feb4.061731.28426@ccu.umanitoba.ca>
Sender: mir@chorus.fr
Reply-To: mir@opera.chorus.fr (Adam Mirowski)
Organization: Chorus systemes, Saint Quentin en Yvelines, France
Lines: 24

In article <1991Feb4.061731.28426@ccu.umanitoba.ca>, umcarls9@ccu.umanitoba.ca (Charles Carlson) writes:
%% The manual for my 386 motherboard specifically says that I need paged mode
%% SIMMS for memory upgrades.  
%% Are all SIMMS paged mode ?  
%% If not, what is the difference betweeon non-paged mode and paged mode SIMMS?
%% I gather the chips are the same so it must be something in the way they are
%% wired on the board.  

Adresses are multiplexed on a SIMM, in order to limit the number of
wires and also because that reflects the internal matrix structure of
the chip. You first provide the upper half, then the lower half of the
address. The RAS and CAS pins are used for signaling.

Page mode means that you don't need to give the upper half again when
changing only the lower part of the address. That cuts the access time
considerably. In conjunction with memory interleaving (having consecutive
adresses in separately adressable banks) and memory caching, page mode
is today technology used to avoid memory access bottlenecks.

I think that SIMMs are all page mode, but I am not a specialist. I never
saw SIMMs advertised as specifically page mode capable.
-- 
Adam Mirowski,  mir@chorus.fr (FRANCE),  tel. +33 (1) 30-64-82-00 or 74
Chorus systemes, 6, av.Gustave Eiffel, 78182 Saint-Quentin-en-Yvelines CEDEX