UnixWare 2 Technical Overview - page 6 of 48

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UnixWare 2 will support both symmetric (all processors of the same time) and asymmetric (different processors) hardware configurations. SMP is the most popular. So far, we have seen 12 pentiums in a Tricord machine - the limiting factor will be the hardware rather than software.

In an ideal world, adding a second processor would double the "performance" of your machine (100% scalability). However this isn't possible for two reasons - there will always be an overhead in managing the processors and the rest of the hardware (disks, buses etc.) may be a limiting factor. UnixWare 2 has a scalability factor of 85% up to eight processors. No other vendor can come close to this figure. Also, UnixWare 2 has a near linear scalability where other vendors will tail off (we have even heard that NT loss' performance upon adding processors!).

As well as this raw performance lead, this give UnixWare an unmatched price/performance over all the competition. (Benchmarks aren't discussed in this talk but in another)

To make best use of the MP hardware, the kernel has been fully threaded and is fully preemptable. This allows CPUS to continue working whilst waiting for I/O.

At an application level, programmers can make use of the threads library to make full use of the MP hardware.

(note that applications will work very well without being threaded, but a single process will be bound to a single CPU and so with a few, large processes, you aren't taking full advantage of the hardware)

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