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From: dan@rna.UUCP (Dan Ts'o)
Newsgroups: comp.sys.ibm.pc
Subject: Extended memory on AT ?
Message-ID: <630@rna.UUCP>
Date: Fri, 29-May-87 20:33:48 EDT
Article-I.D.: rna.630
Posted: Fri May 29 20:33:48 1987
Date-Received: Sun, 31-May-87 11:46:35 EDT
Organization: Rockefeller Neurobiology
Lines: 22


	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 ?

	Any other ideas ? I think ramdisks and DMA'ing memory back and forth
would both be too slow. I believe we need either direct access or bank
switching. I guess we could always use protected mode access. Yuck (Does
any C compiler or subroutine library support this ? We use Microsoft C)

	Thanks.
				Cheers,
				Dan Ts'o
				Dept. Neurobiology	212-570-7671
				Rockefeller Univ.	...cmcl2!rna!dan
				1230 York Ave.		rna!dan@nyu.arpa
				NY, NY 10021