> EXDAMS [...] a thought experiment Ah, good point. > "generally practical for two or three decades" [...] the first practical products I was thinking of "we

> EXDAMS [...] a thought experiment Ah, good point. > "generally practical for two or three decades" [...] the first practical products I was thinking of "we now know how to do this" (snapshot and replay (and input log)), rather than "and it's a product". Which seems sometimes valid, and sometimes not. We know how to make a 4K/eye VR HMD with existing parts, and it's simply a market failure that one's not on my desk. But for other things, "know how to do it, sort of, in a lab" and "know how to do it, practically, for real" can be greatly separated in time and effort. > first practical products were UndoDB and VMWare My very fuzzy recollection is DEC alpha had a reversible debugger in the late 1990's? - but I'm not finding it.