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From: alien@cpoint.UUCP (Alien Wells)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Memory, 32-bit vs 16-bit
Keywords: Memory, Compaq
Message-ID: <3912@cpoint.UUCP>
Date: 7 Feb 90 13:48:47 GMT
References: <7934@chaph.usc.edu>
Reply-To: alien@cpoint.UUCP (Alien Wells)
Distribution: na
Organization: Clearpoint Research Corp., Hopkinton Mass.
Lines: 44

In article <7934@chaph.usc.edu> asplund@alcor.usc.edu (Daryl) writes:
%1.  I was told that if I added a 16-bit memory expansion card 
%(using a slot) that the memory would not be linked contiguously 
%with the current 2Mb that is on the 32-bit board; thus not 
%allowing me to use one memory manager/driver to access all the 
%extended/expanded memory.  The reason given for this is that 32-bit
%memory works completely differently that 16-bit, therefore it 
%would not all be seen as one "chunk" of memory.  IS THIS CORRECT? 

This seems to be total nonsense.  What may be happening is that the Compaq
memory board address decoder may be intercepting more addresses than it is
using (in case you are using larger simms or a daughter card), but the 386
chip has an on-board MMU that can remap your memory any way you want (and
there are lots of available products that use can use to take advantage of
this).

%2.  As the Compaq 32-bit expansion card (connects to the current 
%32-bit card) is about $700.00, does anyone know of any other 
%makers of expansion cards that connect DIRECTLY to the Compaq 
%supplied 32-bit memory card?

This is the real cost of private memory busses.  You do get increased 
performance, but the price is incompatibility with any standard.  You aren't
even guaranteed to be able to use expansion cards from other Compaq models.

Compaq is big enough that there may well be compatible board manufacturers,
but I don't know anything about them.

>3.  If I could get a 16-bit card to work (i.e. all memory 
>accessible contiguousness), would I have to use static column ram 
>as is on the 32-bit card?  Or would I be safe using DRAM, since 
>the access speed is 16-bit as opposed to 32-bit?

Each board will have its own memory requirements that are independant of any
other board (unless one is a daughter board, or they share controlling circuitry
on the mother board, neither of which is true on a memory board on the bus).

The board you buy will determine what chips you need.  Given the slower bus
access time and the 16 bit path, static column DRAMS are unlikely ...

-- 
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Alien   |	  	 		- a Clearpoint VP
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