On: NAND-16: a computer built from 277,248 NAND gates

[ggm]

He has an exterior model in ground truth: you take a pig, you anaesthetise it and isolate an organ, and you measure flow rate in a live subject.

When the model is shown to be within tolerance of what you can measure in the accepted standard methods right now, you can move over with confidence.

[bmitc → ggm]

That ground truth model is extremely crude though, is it not? A pig is not a human, and it's also not a sick human.