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From: jhb@ecsvax.UUCP
Newsgroups: net.micro.pc,net.micro.apple
Subject: Re: A new IBM-compat from Apple?
Message-ID: <1617@ecsvax.UUCP>
Date: Mon, 28-Nov-83 17:17:56 EST
Article-I.D.: ecsvax.1617
Posted: Mon Nov 28 17:17:56 1983
Date-Received: Wed, 30-Nov-83 03:15:14 EST
References: denelcor.219
Lines: 34





Since I like my job, I can't comment on the speculations regarding
MacIntosh's features or prices.  I thought I'd clarify how Apple is
making its machines IBM PC compatible.

To achieve compatiblility the Apple needs:

        - Disk drives that work
        - A new microprocessor
        - A different memory configuration

All this is provided on something like the CP/M cards out there by
telling the 6502 to go to sleep and substituting a new processor.  The
hardware still knows enough to call on the 6502 for I/O.

Emulating a PC is a little tougher, though, because one wants PC disks
to run on the system.  Well, the PC uses the index holes on diskettes
(it's hard sectored).  Apple diskettes are completely soft-sectored,
so Apple doesn't bother to install the extra hardware necessary for
hard-sectoring.  This makes reading PC disks a bit tough.

The solution is to plug in a box that has the appropriate disk drives
in it.  Apple has announced that Rana will be building these boxes.
The drives will be able to read either Apple or PC disks.  The box
will also contain the new processor, etc.

Now, that's how it will work in the Apple II and III.  I leave it as
an excercise for the student to guess how it will work for Macintosh.

- Joe Budge
Apple Computer