The National Enquirer reports at 5:48 PM -0700 6/28/04, Brian L.
Matthews wrote:
> > And, yes Classic (OS 9) is an emulator under OS X, just like Virtual PC.
>
>No, it's not. Virtual PC has to emulate the processor, Classic
>doesn't (for a PowerPC application, for a 68k application it does,
>but the same thing happens when booted into OS 9).
It's a matter of semantics, but I'm glad someone corrected the misstatement.
The Classic Environment is **not** an emulator.
<technical warning>
To quote Apple's Mac OS X documentation:
To the Mac OS 9 operating system that it hosts, Classic appears as
a new hardware platform. It implements hardware services using the
Mac OS X kernel environment (particularly the I/O Kit). The Classic
environment is not an emulator; Mac OS 9 runs natively in it.
An emulator converts hardware calls from one language/platform to
another. For example, Windows doesn't run on Mac hardware, so Virtual
PC emulates PC hardware so that Windows can run on the Mac.
The Classic Environment is actually a "hardware abstraction layer."
OS 9 runs on Mac hardware, and was in fact written for Mac hardware.
But since you can't boot into two operating systems at the same time,
one of the two OSes has to be "in control" of the hardware.
Classic approximates the underlying hardware of your computer, and
then OS 9 loads on top of that hardware abstraction layer. Any
hardware access needed by OS 9 running in Classic is then funneled
through OS X. (This allows OS X to manage all hardware access.) For
example, when a Classic application accesses the Ethernet port on
your Mac, what's really happening is that the Classic application is
accessing the "Ethernet port" of Classic, which is then tunneled
through Mac OS X to the actual Ethernet port. So remember, that
Classic uses the OS X AppleTalk. You should have AppleTalk turned on
in both Systems.(??)
The key point here is hardware vs. software. To put it (overly)
simply, emulation is used to make something run where it can't,
whereas hardware abstraction is used to allow two compatible things
to run cooperatively. Although Virtual PC and the Classic Environment
appear to operate similarly from the user's point of view, how they
do what they do is much different.
<end of technical description>
If your computer can boot into OS 9:
Both as a Classic system environment and as a "native" OS 9 boot
system, there is no difference between a "Classic" System Folder and
a "native" System Folder; they are one and the same.
You can copy it to your heart's content, and if you put it on an OS X
system and try to boot Classic, and it needs some special files to do
so, the OS X system will put what it needs into the System Folder
before booting it; doing so does **nothing** that affects booting it
into "native" OS 9. However, not all of OS 9 runs when it is being
used as Classic. Some of OS 9's functions are subsumed by OS X.
See:
<http://developer.apple.com/techpubs/macosx/Essentials/SystemOverview/
index.html>
Go to: Installation and Integration --> The Classic Environment
Bob
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