The chip only has 8 cores (1 tile)
The chip is special which does have USB
The chip does have pin U19 mapped to the debug header (startKIT Schematics)
startKIT provides a single programmable 500 MIPS xCORE tile with eight logical
cores. All the digital I/O have been brought out to pins providing many combinations
of peripherals to be integrated with the startKIT board. The A8-DEV board
also includes an integrated debugger.
From the startKIT Hardware Manual
Watch this video, at about 1:15, he explains it all
Its 500MIPS xCORE multicore microcontroller has eight 32bit logical cores that perform deterministically, making startKIT an ideal platform for functions ranging from robotics and motion control to networking and digital audio.
From the startKIT Home page: http://www.xmos.com/startkit