gwern comments on An interesting, novel approach to designing computer processors - Less Wrong

3 Post author: D_Alex 21 February 2012 02:37AM

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Comment author: gwern 21 February 2012 06:37:22PM 0 points [-]

The OP seemed to indicate the errors come from the logarithmic approximation and using orders fewer transistors, forfeiting exactness. What is analogue about this? Or does analogue mean something different than I thought and simply refers to there being error-bars on each calculation?

Comment author: Dmytry 21 February 2012 11:03:37PM 2 points [-]

the only way you calculate logarithm or exponent or indeed anything with 1 transistor is by making an analogue circuit.

Comment author: pengvado 22 February 2012 01:33:35AM *  1 point [-]

Here's the patent, since I couldn't find any other detailed documentation. It describes two separate implementations:
* Digital, storing log(x) as a fixed-point number and performing ordinary digital arithmetic on it.
* Analogue, storing x as floating-point with digital sign and exponent but analogue mantissa. It then describes some mixed analogue/digital circuits to perform the requisite arithmetic.

The slides linked in the OP are about the digital one, and only once mention the possibility of analogue as an intuition pump. I don't know which one the quoted performance numbers are for.