Xerox Alto on ebay (not mine!)

I have to disagree. Only last Wednesday I was single shotting my simulator and the real hardware to find where they diverged. It showed up the fault after a few hundred instructions instead of running for a half a second before crashing (by which I mean the hardware stopping because it detected the loading of an instruction where one of the digits was not binary coded decimal). I am also working on a deeper simulator which models the actual gates of the computer and their interconnections. The source code of this describes the computer in great detail and I would say would be better than real hardware from some purposes. It will also allow monitoring of signals with a virtual oscilloscope and maybe one day, the introduction of simulated faults to test the brains of anyone mad enough to want to see how the original engineers would tackle faults. One day it might even have a 3D graphical interface where you can walk around the machine, open covers and connect your virtual 'scope and the original sounds recorded from the real hardware, like the drum running up. Roger Holmes ICT 1301 + many Apples - ][, ///, Lisa, and Mac up to the latest MacBook Pro.