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Path: utzoo!mnetor!seismo!husc6!necntc!gordon!davido
From: davido@gordon.UUCP (David Ornstein)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Extended memory on AT ?
Message-ID: <19@gordon.UUCP>
Date: Sat, 30-May-87 10:37:39 EDT
Article-I.D.: gordon.19
Posted: Sat May 30 10:37:39 1987
Date-Received: Mon, 1-Jun-87 05:45:05 EDT
References: <630@rna.UUCP>
Reply-To: davido@gordon.UUCP (David Ornstein)
Organization: Access Technology Inc., S. Natick MA, 01760
Lines: 36

In article <630@rna.UUCP> dan@rna.UUCP (Dan Ts'o) writes:
>
>	I would imagine this question has been covered before - Sorry.
>
>	We have an application that requires fast access to 4Mb on a PC/AT.
>What is the best way to do this (from a C program). I have heard that the
>Intel Above Board Memory Spec is a bank switching scheme whose details are
>kept secret but it apparently is possible to figure out. Is this information
>available somewhere, or at least a subroutine library that can grab large
>chunks (60kb) fast by bank switching ?
>

The Lotus-INtel-Microsoft extended memory spec (LIMEMS) is a public
system that allows swicthing 64K (it might be 128, I don't remember)
chunks of memory in and out of a window in the board's address space.

There are two kinds of extension memory for the PC: extended and expanded.
Expanded memory is the type that uses the bank-switching mechanism you
have heard about.  Extended memory is simply more memory added to the 
system's normal address space.  MSDOS can't utilize extended memory, while
many of the larger applications s/w packages (e.g 123) can access expanded
memory.

Most expansion memory cards for the pc allow you to configure the on-board
memory as all one or some of both types.  I know this is true of the intel
Above Boards...

-- 
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David Ornstein		"Never join a religion that has a water slide."

Internet:	davido@gordon
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