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Microsoft Sees Linux As Bigger Competitor Than Apple
Facetious writes "It seems Microsoft doesn't believe the data from Net Applications regarding Linux any more than Slashdot readers do. In a recent presentation, Microsoft CEO Steve Ballmer showed a slide showing, from Microsoft's internal analysis, that Linux client use is clearly ahead of Apple's."
Actually, OSX is certified Unix.
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Do you know whether it's POSIX-compliant?
Yes.
Is it proper to refer to it as a "Unix" or is it a "Unix clone" or "Unix-like system" like Linux?
OS X is a certified UNIX.
I'd also be interested in anything explaining why they went with a Mach microkernel and whether that has any non-negligible impact on performance (i.e. message-passing overhead, switching from kernel to userspace, etc). I'd appreciate anything you are able to explain since I'm honestly rather ignorant about OSX.
The message passing overhead is fairly high compared to other systems like Linux or other BSDs. Unlike monolithic kernels, the Mach based one that Darwin (The UNIX part of OS X) uses actually has to do a full context switch when one makes a system call. That can be slow, especially with TLB flushes and such.
Wikipedia and Apple have some pretty good docs on how it works.
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What if they offered Linus Torvalds a billion dollars for the trademark and the copyright to his code?
The Linux kernel is only a part of a GNU/Linux system. Almost everything, including the kernel, has been published under the GNU General Public License (cf. GNU).
Linus Torvalds is still the figurehead of Linux kernel development, but even if Microsoft would manage to purchase all rights to the Linux kernel, that would have little impact, because the Linux kernel has already been published under the GPL, which makes it legal to modify it and keep it under the GPL forever, no matter if there also would be a proprietary version.
The GNU project (which contains all free Linux software including the Linux kernel) also develops their own Mach-based kernel, called "Hurd" (the OS would be called GNU/Hurd then).
Even if Microsoft would manage to purchase Richard Stallman, the head of GNU, it would have little impact on free software development, since all code that already exists can be forked away before any proprietary branches would emerge.
Do you know whether it's POSIX-compliant
POSIX is a subset of the Single UNIX Specification. Any system that is UNIX(tm) is also POSIX, but not every POSIX system is UNIX.
I'd also be interested in anything explaining why they went with a Mach microkernel and whether that has any non-negligible impact on performance
Because, in 1988, when they designed the system, Mach was the state of the art. NeXT used it and so did OSF/1 and a few other systems. Everything since then has been incremental improvements. There is almost no message-passing overhead in OS X because Mach is just used as a hardware abstraction layer, and most of the stuff runs in the BSD single server.
If you want to know more about how OS X works at a system level, Amit Singh has written an excellent book about it.
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Actually there is far more money in clients than in servers. The profit margins on server software (and hardware) tend to be higher per sale, but in terms of both gross revenue and total profit clients wins hands down.
Heck, that's why Microsoft is the 800 pound gorilla of software. Windows makes truly ridiculous amounts of money, and the fact that Microsoft controls the end user experience at a very low level gives Microsoft a great deal of leverage.
Microsoft has a very profitable server software division, but its profits are barely a third of Microsoft's Client division, and MS Office (another piece of client software) generates nearly as much profit as Windows.
The client rules, plain and simple.
Ok, in a nutshell:
OS X uses Mach's CPU scheduling and memory management. The rest of the code in the kernel (the process model, the network stack, etc) is a combination of *BSD code, code developed in-house (like the IOKIt), and vendor-supplied code (like the video drivers from NVIDIA and ATI). Below the GUI, there's code from many, many projects, such as the shells, Python, Ruby, sendmail, and so on. The 3D graphics library is OpenGL, with in-house additions. The 2D graphics library is all Apple-developed code, except for some licensed implementations of pieces like the JPEG2000 decoder.
If you have the developer tools installed, have a look at /Developer/Documentation/Acknowledgements.rtf for a full list of the organizations from whom Apple has licensed code that they include in OS X.
-jcr
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