Reproducing old machines with newer technology

[tony duell]

> That wasn't all that uncommon in the microprocessor world--once the
> price dropped sufficiently, doing multiuser applications by giving each
> user their own CPU was practical.  Molecular was another outfit that did
> practically the same thing.
> 
> Dual-CPU setups, where the "weaker" of the two CPUs was in control of
> the "stronger" one were even more numerous--just consider the number of
> "add in" processor cards for the PC archicture.  68K, NS32xxx...you name
> a CPU, it's probably been on an ISA card.

The common UK example is the BBC micro. It was a complete useable 
6502-based computer, but could have a 'second processor' added 
via an interface known as the 'tube'[1] The 6502 in the BBC micro handled
I/O functions, while user programs ran on the second processor. The ones
I know of are
6502 (ran BBC software including BBC BASIC, but faster than the plain BBC)
Z80 (ran CP/M)
32016 (ran something called PANOS)
ARM 

There were also a couple of (fairly rare) Acorn machines which consisted of 
a BBC B+ mainboard in a case with a built-in monitor and disk drives and
a second processor board. The ABC (Acorn Business Computer) had a Z80, the
ACW (Acorn Cambridge Workstation) had a 32016

[1] So called (officially) because it provided a 'tube' to pass information between
the 2 processors. But of course 'Tube' is a common name for the London Underground
(subway) and 'Bus' is anotherr form of public transport. As a total aside, the system
bus on the Tatung Einstein was called the 'Pipe', presumably a pun on 'tube', for all
that machine never took second processors.

-tony