[wplug] virtualization/emulation (was WINE & MAYA PLE)

[Patrick Wagstrom]

On Fri, 2006-01-27 at 20:00 -0500, Matthew J. Hughes wrote:
> I think Patrick mentions that there is a free vmware player out now. I 
> heard vmware rocks but alas, I have not been able to use it until now. 
> There is a comparison of the various emulators over at 
> http://wikipedia.org/. Bochs is rated as very slow, others are faster. I 
> was wondering if anyone has used bochs?
> -matt

One of the key things to look at is whether the product does
virtualization or emulation.  Bochs and QEmu (for the most part) are
emulators, meaning that they translate non-native instructions to the
platform you're running on.  This means that Bochs and QEmu both run on
many different architectures and can emulate a wide variety of other
platforms - for example running PowerPC apps on a SPARC, or emulating an
Itanium on a Pentium.  This translation is slow, but can be effective --
it's what Rosetta on the Intel based Mac computers does[1].

Virtualization relies on the systems having the same instruction set.
It runs through the instructions as normal until it reaches a privileged
instruction, it then traps the instruction and reroutes it.  This is why
VirtualPC on Windows and VMWare run so much faster - they can just run
native code.  It's also why applications that don't use privileged
instructions much, such as mathematical simulations run quite fast when
virtualized, while those that access the disk frequently (a privileged
instruction) run very slowly.

If anyone is interested, I've got VMWare Workstation on my laptop.
Bring along some installation medium (and license if applicable) for
your OS of choice and I'll make a VMWare virtual machine for you the
next time I'm at a WPLUG meeting.

--Patrick

[1] - In the most pure sense, Rosetta is halfway between and emulator
and virtualization - more in line with Java and .NET CIL applications.
Basically it runs through the program and translates the instructions
from PowerPC format to i386 format as it goes.  Frequently accessed
instructions are only translated once, increasing the speed of those
instructions.