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From: bobp@amiga.UUCP (Robert S. Pariseau)
Newsgroups: net.micro.amiga
Subject: Amiga shown with 68020
Message-ID: <310@amiga.amiga.UUCP>
Date: Thu, 21-Nov-85 14:41:38 EST
Article-I.D.: amiga.310
Posted: Thu Nov 21 14:41:38 1985
Date-Received: Sat, 23-Nov-85 05:50:15 EST
Reply-To: bobp@snake.UUCP (Robert S. Pariseau)
Organization: Commodore-Amiga Inc., 983 University Ave #D, Los Gatos CA 95030
Lines: 46


TITLE:  Amiga shown with 68020

At Comdex yesterday, Computer System Associates (CSA) showed their
68020 board for the Amiga.  This board includes a 68020, a 68881 math
processor, and 256K bytes of 32-bit bus RAM.  The board replaces the
68000 in the Amiga, plugging into it's socket.  The board fits under
the Amiga FCC shield.  No release date was announced.

The board was demonstrated using a pre-release version of the new
Amiga V1.1 system software.  The V1.1 software is compatible with
the 68010 and the 68020 processors.  Application programmers wishing
to take advantage of such products should be sure to use the Exec
GetCC() function to get the processor condition codes.  (GetCC() handles
the differences between the processors such as the fact that MoveSR
is an invalid user mode operation in the 68010 and 68020.)  In addition,
you should be sure to NOT use the upper 8 bits of a pointer for storing
unrelated information, since the 68020 uses all 32 bits for addressing.

For those doing systems work, Exec maintains flags in the AttnFlags
field of ExecBase which describe the type of processor in your
machine.  Exec's coldstart procedure will update certain library entry
vectors as necessary to maintain compatability.  If you write code
that uses the Supervisor() function, keep in mind that your stack frame
is processor dependent.  Use the new SuperState() function for
processor independent supervisor mode entry.

V1.1 ROMWack will correctly display information for 68010/20 address
and bus errors.

When the 68020 is detected during coldstart, its instruction cache is
enabled.  This has implications for programmers writing self-modifying
code.

The new Exec function TypeOfMem() should be used by programs wishing
to know whether a given address is in Chip memory or Fast memory.  This
function will insure compatability with future Amiga architectures.
It should be used instead of assuming that certain fixed address
boundaries define the break between Chip and Fast memory.

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Computer System Associates, Inc.
7564 Trade Street
San Diego, CA 92121
(619)566-3911