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From: gert@nikhefh.UUCP
Newsgroups: comp.os.minix
Subject: Re: Minix-ST context switch (Really: Address Translation in the ST)
Message-ID: <394@nikhefh.UUCP>
Date: Wed, 30-Sep-87 04:28:09 EDT
Article-I.D.: nikhefh.394
Posted: Wed Sep 30 04:28:09 1987
Date-Received: Fri, 2-Oct-87 01:47:00 EDT
References: <10647@orchid.waterloo.edu> <499@ast.cs.vu.nl> <790@sugar.UUCP> <850@atari.UUCP> <827@sugar.UUCP>
Reply-To: gert@nikhefh.UUCP (Gert Poletiek)
Distribution: comp
Organization: Nikhef-H, Amsterdam (the Netherlands).
Lines: 27

In article <827@sugar.UUCP> peter@sugar.UUCP (Peter da Silva) writes:
>OK, already. The ATARI ST does not do address translation. All I have to say
>then is that the available documentation is even worse than I thought. Because
>that's how I interpreted teh Abacus manual.
>-- 
>-- Peter da Silva `-_-' ...!hoptoad!academ!uhnix1!sugar!peter
>--                 'U`  Have you hugged your wolf today?
>-- Disclaimer: These aren't mere opinions... these are *values*.


The Atari ST does not have address translation in a form that would be useful
for solving context switch problems. It does however have some form of address
translation. In the ST there are one or two memory banks. When two banks are
present the ST can handle banks of different size, e.g, bank 0 may hold 512KB
and bank 1 may hold 2M. The ''MMU'' then takes care of mapping the banks such
that it appears as one contiguous block of memory.

(-- This is not according to any book, but according to a disassembly of the
 ST roms I made )


Gert Poletiek

NIKHEF-H, Dutch National Institute for Nuclear and High Energy Physics
          Kruislaan 409, P.O.Box 41882, 1009 DB Amsterdam, The Netherlands
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