"Frankly, I think it's a piece of crap," Torvalds writes of Mach, the microkernel on which Apple's new operating system is based, with additional elements from the FreeBSD version of Unix. "It contains all the design mistakes you can make, and manages to even make up a few of its own."
Torvalds' comments promise to upset not just Apple fans but also some quarters of the free software movement. The Mach microkernel is also being used as the core of Hurd, a kernel project from the Free Software Foundation that will be an alternative to Linux as the heart of the GNU (Gnu's Not Unix) operating system, originally devised by free-software advocate Richard Stallman.
The criticism comes in a chapter of "Just for Fun" where Torvalds tells that, on arrival in Silicon Valley in early 1997, Apple Chief Executive Steve Jobs invited him to join Apple and help develop OS X. He says Jobs also wanted him to help attract open-source developers to the project.
The remarks will particularly sting Apple because the company has widely publicized the fact that the core of its new operating system is, like Linux, based on the Unix operating system and was developed on open-source software.
The Mach microkernel was created at Carnegie Mellon University in 1985 and has been incorporated into a number of commercial operating systems, including IBM's OS/2 on certain systems and Apple's OS X. Torvalds says that as developers have tried to improve the Mach microkernel it has become hugely complicated and convoluted.
Bumps and starts
OS X has not been unanimously applauded since its launch. Shortly after it was released to the public two weeks ago, users questioned the lack of support for certain peripherals, particularly CD-rewritable and DVD-recording drives.
Torvalds writes that, even back in 1997, he foresaw compatibility problems between the new operating system and older applications, due to a lack of memory protection--a safeguard that stops applications influencing each other and the operating system--in old Mac applications.
According to Torvalds, Jobs assumed Torvalds would be interested in joining Apple's mission to capture more of the PC market from Microsoft, rather than continuing to concentrate on Linux. "I don't think Jobs realized that Linux would potentially have more users than Apple, although it's a very different user base," he writes.
Apple representatives were not immediately available for comment.
Staff writer Will Knight reported from London.