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From: dclemans@mntgfx.mentor.com (Dave Clemans)
Newsgroups: comp.sys.atari.st
Subject: Re: Mega STs
Message-ID: <1987Nov10.135453.2113@mntgfx.mentor.com>
Date: Tue, 10-Nov-87 16:54:50 EST
Article-I.D.: mntgfx.1987Nov10.135453.2113
Posted: Tue Nov 10 16:54:50 1987
Date-Received: Fri, 13-Nov-87 07:20:40 EST
References: <4114@garfield.UUCP>
Organization: Mentor Graphics Corporation, Beaverton Oregon
Lines: 39

There are two major causes of incompatibility with the blitter rom's
(as used in the Mega ST's)

Essentially all of the "undocumented" low memory locations have moved.

A MAJOR bug in the read portion of the floppy driver was fixed.
This bug had two symptoms that people might have encountered:

    error status might not be correctly reported after a read that
    got an I/O error

    If running a program that used BIOS calls to directly access the
    floppy (for performance), multi-sector reads were not reliable

(assuming that the BIOS listing ATARI sent me as part of the developers
kit accurately represented the old ROM's, the bug was caused by mis-using
a WD-1772 sector read command).

From what I've heard, the floppy read bug fix is what has caused most
compatibility problems; it seems some manufacturers of copy protected
software (mainly games) based their copy protection on a side-effect
of the bug.  Based on my experience the other areas aren't as major;
the only packages I know of that were affected were the "twister"
formatter that came from STart and possibly GFA basic.

=============

How much memory you want depends on what you do now, and what you
might want in the future.  My system (4 megabytes) normally runs
with slightly under 2 megabytes free.  The rest is taken by a 800K
ram disk, a LARGE disk sector cache, a large printer buffer, auto-loaded
programs, desk accessories, etc.  The whole conglomeration boots in
under 30 seconds, including the time to load about 400K of files into
the ramdisk.

There are also software packages that want memory; the laser printer driver,
Smalltalk-80, OS-9, IDRIS, etc.

dgc