Right, many of the early (~1975) era microcomputers were bus backplane machines, where the CPU boards were just one of the "bus masters" and designed to coopera

Right, many of the early (~1975) era microcomputers were bus backplane machines, where the CPU boards were just one of the "bus masters" and designed to cooperatively share the mostly passive backplane. (ex: ss-50, s-100). It was fairly common to attach z80's and the like as secondary co-processors, as well as allowing peripheral boards direct access to RAM/etc via DMA. So, while I'm not aware of anyone building a machine using multiple 8086's its was pretty common to put 8086's and z80's together in the same machine, nevermind the 8087 was effectively a second processor as well until it was integrated in the 80486 DX. Although looking at a few of the schematics on http://www.s100computers.com/index.html http://www.s100computers.com/index.html I don't see anyone actually using the 8086 #LOCK pin even if they are running the processor in max mode to gain the extra control lines for the S-100. Probably because few people were thinking about full _symetric_ Multi Processing, vs heterogeneous machines, which were fairly common. Z80 boards existed for a lot of machines (I had one for my apple II+), as did various other combinations.