On Aug 16, 2007, at 11:10 AM, Peter Laws wrote:
> The current "hot" emulator is Parallels (http://www.parallels.com/).
> It runs a virtual machine onto which you load your favorite version of
> MS-Windows (a legal copy of course!). No muss, no fuss. It may
> support loading Linux distributions as well.
I'll throw in my two cents by offering some clarification. There are
really three distinct classes of products -- emulators,
virtualization and dual-boot...
-- Emulators --
SoftWindows, SoftPC and VirtualPC are emulators that run on the old
68000 and PowerPC machines.
SoftWindows was a Windows emulator (emulated Wind 3.1). It took
Windows system calls and cloned the functions. So it not only
emulated the x86 instruction set, it also emulated the Windows
operating system.
SoftPC and VirtualPC are actually emulators of the PC hardware, they
do not emulate Windows. You actually install Windows for the
emulator to run. You can run Win95, Win2k, etc on them, also
including various x86 based Linux distros.
(A couple of years ago, Microsoft bought the company that created
VirtualPC and ported VirtualPC to run on x86 machines. This allowed
a WinNT computer to concurrently run WinXP, for example.)
Crossover, which is derived from the open sourced Wine project
(http://www.winehq.org/) is a Window emulator but runs native code
without translating machine code. I.e., it emulates the Windows OS
but does not have to emulate the machine code.
On Macs, the software emulators (whether they emulated Windows, or
emulated the x86 hardware) run very slowly as you can imagine. Each
x86 instruction has to be interpreted into either a 6800 machine code
or a PowerPC machine code, or, in the case of Wine and Crossover,
"just" (HI HI) emulating the system calls.
-- Virtualization --
Software such as Parallels' "Desktop for Mac" and VMWare's "Fusion"
are virtualization products and are completely different animals from
emulators. They neither emulate the machine code, nor do they
emulate the Windows operating system.
These programs make use of hardware that supports virtual machines.
Each virtual machine thinks it is running on real hardware.
Virtualization products do not translate code. The current
Macintoshes have Intel Core Duo processors in them and they support
virtualization. They present an interface that looks like a
completely separate x86 PC and you can install different versions of
Windows or different Linux distros into this virtual machine, as if
you are installing them into a standalone x86 computer.
It is like having multiple computers but using a single monitor with
picture-in-picture screens watching each virtual machine. They can
also be operated in "full screen" mode (such as the Coherence mode in
Parallels "Desktop for Mac"). When you are in full screen mode, the
display looks just like the screen of a Windows computer, except that
with a single keystroke, you can switch to look a MacOS desktop
instead. You can operate two monitors and one displays the MacOS
desktop wile the second monitor displays the Windows desktop.
The MacOS applications and Windows program can run concurrently.
They don't even know that each other exists, except when they want to
both access a sound card.
-- Dual Boot --
Boot Camp is yet another different animal altogether from the above
two classes. Boot Camp is really just a tool (with drivers, etc)
that allows you to easily partition your hard drive, with Mac OS X on
one partition of the hard drive and with Windows XP or Vista on a
different partition on the hard drive, and it comes with a simple
mechanism to boot into either partition when you restart the
computer. Many people who run Linux are already familiar with this
process since a lot of them are already dual booting between Windows
and Linux.
The more important thing about Boot Camp is that it provides the
necessary Windows drivers for the built-in sound cards, built-in web
cams, USB, Firewire, etc that comes with Macintoshes.
With BootCamp, you cannot run both OS at the same time, but only one
OS at a time. With emulation and virtualization, MacOS applications
and Window programs can be executing side by side.
----
A modern Macintosh such an iMac is pretty much built using the same
Core Duo Intel processors that modern Windows machine run on (if they
are using Intel rather than AMD processors).
The MacPro, for example is an 8 core computer, made up of two 3.0 GHz
Quad Core Intel Xeons. The difference is that the modern Macs will
run both Mac OS X and Windows, whereas you cannot run Mac OS X on a
Core Duo machine that you buy from Dell or HP.
The next time you hear someone complain of not being able to do
contests because they are using a Mac, just hit them on the head with
a large hammer. You won't be doing any more damage to an already non
functional brain :-).
73
Chen, W7AY
P.S., there are actually are other programs for Mac-to-Mac
emulation. "Classic" allows you to emulate MacOS 9 on a Mac OS X
machine that runs a PowerPC processor. "Rosetta" is a just-in-time
interpreter that allows you to run Mac OS X programs that are written
only for the PowerPC architecture to also run on the Intel architecture.
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