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From: wescott@Columbia.NCR.COM (Mike Wescott)
Newsgroups: comp.sys.ncr
Subject: Re: accessing Multibus shared memory
Message-ID: <1896@sauron.Columbia.NCR.COM>
Date: 15 Jan 90 16:43:41 GMT
References: <180@seachg.UUCP>
Sender: news@sauron.Columbia.NCR.COM
Reply-To: wescott@micky.Columbia.NCR.COM (Mike Wescott)
Organization: E&M-Columbia, NCR Corp, W Columbia, SC
Lines: 23

In article <180@seachg.UUCP> jalsop@seachg.UUCP (John Alsop) writes:
> We have an old Multibus communications controller (actually a single-board
> microcomputer made by Heurikon) which uses shared memory to interface with
> the Multibus host. We are trying to get this working on a Tower 600.

> The Multibus memory addresses to which this board responds are decoded by a
> custom PAL on the board. The problem we have is that we don't know what this 
> address range is, other than that it is a 24 bit address.

> We tried writing a simple C program that scanned through "/dev/kmem"
> looking for a fixed data pattern which we know is on the board, but no
> luck.

Most of the multibus memory space is not normally mapped in, hence
it cannot be accessed on the 600 without special help from the kernel.

You'd need to write a driver that allocated some kernel address space
and mapped that space to point into the multibus address space.  More
specific information on this procedure should be in the document on
writing device drivers.
--
	-Mike Wescott
	 mike.wescott@ncrcae.Columbia.NCR.COM