Zane H. Healy wrote:
  I'm not aware of one.  Here are the Big Iron
emulators that I am aware of:
 
http://www.aracnet.com/~healyzh/bigironemu.html 
What defines 'big'? Raw horsepower, or physical size, or something else?
I'm just thinking that there are probably lots of emulators of older (1950s
and 1960s) machines around - big iron in their day, but not exactly quick by
the standards of 1970's hardware.
cheers
Jules