[B1FF_PSUVM]

I believe so, the comp. arch. textbooks were pretty emphatic on the description of the CDC 6600 as "full of peripheral processors", e.g. for I/O and printing, etc. Deliberately, not something tacked on later as an afterthought.

[dfox]

I cannot find any information about whether one of the peripheral processors in CDC 6600 (which were full-blown CPUs, not glorified DMA engines as in Cray-1 or System/360) has some kind of system management role. On the other hand Cray-1 needs not one, but two frontend computers to work (one is DG Nova/Eclipse supplied by Cray which actually boots the system and second one has to be provided by customer and is essentially an user interface)

[vajrabum]

The peripheral processors were integral to the CDC 6600 and it's successors (6400,6200,6700,7600, and Cyber 70 series) built inside the same mainframe cabinet. In the 6000 and Cyber 70 series There were '10 of them' that shared the same ALU with a barrel shifter that would shift 12 bits after each instruction. That shift would load the registers for the 'next PP' in a round robing fashion. They were pretty primitive. There were no index registers so self modifying code was a regular thing and polling was the only method of IO supported at least at first. I think the later models did support some sort of DMS. The PPs did have access to the 60 bit main memory and there was an instruction exchange jump or XJ which would load the register block and switch between user and supervisor modes.

[pinewurst]

What do you mean? The CDC OSes actually ran on the PPs and for all intents and purposes managed the system. The two-headed video console was hardwired to a PP as well, and used to managed the system.