Thanks for the detailed comment, Kragen. I didn't think anyone remembered xfractint :-) I think your analysis is correct, although I'll need to investigate Henkin-sentence circuits some more
You mention dynamic stages that rely on capacitance - these pass-transistor circuits are a standard technique, written up in books. The key is the nearly-infinite input impedance of MOS transistors, which lets the charge hang around for a while. Interestingly, the Z-80 doesn't use this, so its clock speed can be reduced down to DC, unlike the 6502, 8085, etc that have a minimum clock speed as you say.
Oh, a Henkin sentence is a sentence that asserts its own truth: "This sentence is true" — the opposite of the Liar's Paradox. You can self-consistently treat a Henkin sentence as either true or false: it's true if it's true, and false if it's false. A circuit analogue might be a buffer connected to its own input, or two inverters wired in the fashion you describe: "This sentence is not false."
This last week I've been using the nearly-infinite input impedance of MOS transistors to use LEDs as light sensors, as described in the Yerazunis's MERL paper. I'm not getting speeds anywhere close to the speeds they were reporting, though: closer to Hz than to MHz measurements.
If Xfractint is the "stone soup" fractal program then I remember. :)
Probably the first program I actually remember was a ratty ol' Mandlebrot fractal generator in Turbo Pascal 7.0 from probably around 1994-95 or so. Then I saw programs that were coded by people who actually knew what they were doing and my head asploded. :)
The "stone soup" fractal program is Fractint. Xfractint was my port of it to Unix/X, which was a bit tricky since parts of Fractint were in extremely tight 386 assembler that did crazy stuff like simulating floats with integers for performance.
You mention dynamic stages that rely on capacitance - these pass-transistor circuits are a standard technique, written up in books. The key is the nearly-infinite input impedance of MOS transistors, which lets the charge hang around for a while. Interestingly, the Z-80 doesn't use this, so its clock speed can be reduced down to DC, unlike the 6502, 8085, etc that have a minimum clock speed as you say.