When is the earliest time for an industrial revolution?

I've seen many scenarios about an earlier IR, but my question is: when is the earliest possible time (without going into ASB territory) something akin to OTL's Industrial Revolution can happen? If so, then where?

Song China has been thrown around a lot, but is it possible with a Rome that doesn't collapse, or a stable Muslim caliphate?
 
Any of those could work. Ultimately, you need a revolution in agricultural production and rudimentary industrial production around the same time. Free up labor and maximize the efficacy of centralized production with that labor. Once thats happened, it should be self-perpetuating.

To the first point, an alt-Columbian exhange cannot be underestimated in its value. Vut also just more efficient techniques and tools. To the second, the general body of various proto-industrial inventions... looms, water wheels, pumps, printing presses, etc etc. are quite useful.
 
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