Gosh, that
is an oddity! BTW there's a typo; I'm sure they mean 6100 (made by Harris and Intersil), not 600. But it's a
twelve-bit CPU! And apparently it and the Z80 are under control of the 6502 host system.
http://en.wikipedia.org/wiki/Intersil_6100I took a peek at the linked page, and was startled at what a wide variety of boards OSI offered. Here's a combo board, featuring a 6800, a 6502 and a Z80. Just the thing for an enthusiast from the 1970s who wants to cover all the bases (or can't make up his mind)!
-- Jeff