The real VIP had a 16-bit address space which was mostly unpopulated. The VIP "OS" resided in a ROM which was outside the 4kb of RAM that CHIP-8 can easily access, but you could still manipulate i to point there via repeated addition or, in the case of the font, via the instruction Octo calls "i := hex vx".
I linked the manual, which contains memory maps, earlier in the thread.