Apple's "HD" video has largely been 720p... I don't think they're doing full 1080p AVC decoding on a 1.5GHz PPC, certainly not without serious GPU acceleration of the video decode.
The Mac mini 1.5 GHz running MPlayer/MorphOS does a 720 movie at about 2/3 cpu load. 1080 is possible under some certain circumstances (has beed demoed a while back), but not in a manner that you could say it is an everyday solution.
The inclusion of the XMOS chip is pretty mysterious. It's not a huge expense.. you can buy the four-core version at DigiKey for about $20 (they sell at devkit at $99, including demo board and software). But this is a weird chip... four fairly lower powered cores, each of which runs eight threads. They claim 1600MIPS, but that's going to be peak... every thread in use. There's some weired connection matrix, so you can arrange these things in different orders.. maybe interesting for simple audio processing. But overall, less of a CPU than an ARM Cortex A8 (eg, regular smartphone chip), with the FPU and SIMD units taken out. And there's a slot for this? Weird... though I am curious what they intend to do with this that couldn't better be done with another 400MHz of host processor juice.
The only outstanding feature of the XMOS chip I figured out so far is that the threads are hardware warranted real time. Thus, sub tasks can use RT features even in a non RT envirionemnt. But this surely has its limits once interaction with the Host non RTOS on the host cpu is involved, because then it is again a question of how the interruped triggered by the XMOS gets processed.
And I fail to see the need to include that XMOS chip on the mainboard, a pci(e) card would certainly do as well, for many purposes (when no dma master is required) even a usb extension would work
