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Other than easy construction and asynchrony, what advantages does it offer over p30 and p46 technology? p30 90° reflectors can fit in a 9x23 bounding box and can receive another glider in 30 generations; the stable 90° reflector in Gemini has an 81x70 bounding box and takes 488 generations to recover, so building complex circuits with p30 technology has an obvious advantage.

... and takes 488 generations to recover ...

497 generations, actually. The smallest, fastest 180° reflector takes a mere 106 generations to recover, and Herschel-based circuitry is faster still.

what advantages does it offer over p30 and p46 technology?

• Easier to synthesise and destroy with gliders
• Reflectors are more versatile, thanks to Herschel tracks
• Completely asynchronous, therefore easier to design
• Can emit gliders at any time, as opposed to multiples of 30 generations
• Runs faster in HashLife

If you're still not convinced, try and construct either Gemini or my Phi calculator using only p30 technology.

But the Universal Turing Machine was implemented with p30, so it's certainly practical for computation.

But the Universal Turing Machine was implemented with p30, so it's certainly practical for computation.

The Universal Turing Machine is not universal; it has a finite tape. The only infinite tapes implemented so far use stable technology.

calcyman wrote:The only infinite tapes implemented so far use stable technology.

Not true. The original MRM was implemented using P30 technology, based on Dean Hickerson's Sliding Block Memory. It's all I knew at the time.

Cheers, Paul

Not true. The original MRM was implemented using P30 technology, based on Dean Hickerson's Sliding Block Memory. It's all I knew at the time.

But are they not registers, rather than tapes? They store data in O(e^n) space, rather than O(n) space.

I might admit to the charge that the MRM is not "practical", but nevertheless it is a UC implemented in P30.

Cheers, Paul

but nevertheless it is a UC implemented in P30.

Yes, it is a Universal Computer. Or rather, it would be if it weren't for a glitch at (1330,6620).