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DragonFly BSD 4.0 Released
An anonymous reader writes From the release page: Version 4 of DragonFly brings Haswell graphics support, 3D acceleration, and improved performance in extremely high-traffic networks. DragonFly now supports up to 256 CPUs, Haswell graphics (i915), concurrent pf operation, and a variety of other devices.
Another OS that has dropped support for 32-bit architecture. This is probably not an issue for most users as 32-bit processors are less common these days. If you have an older machine with a 32-bit processor, you can't slap on the latest and greatest *nix OS.
This... specifically the way he felt FreeBSD over complicated threads.
A simple implementation would be "every user space thread has a kernel thread". FreeBSD kind of went to the "lets give a lot of knobs and levers for people to play with." It went to something similar to the old Solaris multithreading model where you can say how many kernel threads for each user thread, or one kernel thread per app, or whatever combination. This added a lot of complexity. Ironically, this happened just as Solaris was moving to a much simpler 1:1 model.
Dillon was worried that it would make it so complicated that only a handful of people could do any coding in the kernel scheduler. This for very little gain as most people couldn't do anything useful with those knobs and levers. He was kind of proven right. FreeBSD kind of stalled out for a bit.
That was the initial reason for the break. Over time, the design diverged to where he added more message passing architecture in the kernel, inspired by the Amiga's design.
What's a "Unix"?
Is it a system based on AT&T code? If so, how much AT&T code has to still be in it.
Yes. Legally, all AT&T derived systems are grandfathered in as part of the License agreement which exclusively licensed the trademark to The Open Group for relicensing to third parties. For example, the transferrable SVR3 and SVR4 source licenses I own as a result of being sold surplus Class C computing equipment by Weber State University under their blanket source licenses mean my port of SVR3 to the Amiga I did for giggles, is legally UNIX.
Is it a system that passes the Single UNIX Specification test suite and whose supplier is thus allowed to license the "Unix" trademark?
Only if they subsequently license the trademark. If so, then it's UNIX. If they don't license the trademark, even if it passes the tests (which must also be licensed from The Open Group), or if they fail to register a compliance statement, and have it certified, it's not UNIX. Mac OS X, for example, is UNIX. iOS on the iPad, iPod Touch, and iPhone isn't UNIX -- and can't be; certain required interfaces are conditionally compiled out, as a space saving measure, and additional user space commands are not compiled for the publicly released versions.
Is it a system with a Unix-compatible API?
No. A system with a Unix-compatible API can pass the VSX, VSTH, and VSRT test suites, but unless the user space is there, it can't pass the VSC test suite, nor can it pass the compilation environment test suite, which include ISO C certification of the compiler and libraries, as well as passing negative assertion tests for namespace pollution on the header files (Linux/glibc/glibc2 have serious header file problems; so do the *BSDs). Android can't pass because it fails on threading API compliance with the VSTH test, partly because of the "Bionic" libc implementation having deficiencies (it would take a small amount of work to pass the VSX tests in that regard, but threads are the biggie).