Notes for the Lifebox, the Seashell, and the Soul - Rudy Rucker

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Notes for The Lifebox, the Seashell, and the Soul, by Rudy Rucker depending on how much RAM the particular machine has. The “random access” aspect of the memory has to do with the fact that each memory cell has an address, and the processor is able to read or write the contents of a cell at any desired address without having to traverse all of the intermediate cells. If necessary, a computer can actually use more memory than it has in its RAM by reading and writing to extra disk, which function as a slower kind of RAM. (To read something off a disk, you need to physically move a read head to a certain address position. Reading from a given location on a RAM chip is more like pulsing a signal into an address wire and getting an answer back right away.) *** How does the processor know how to carry out instructions? This is handled by a tiny program, known as microcode, that is coded right into the processor. Microcode interprets strings of bits as instructions to do things with the registers. The microcode lets the processor behave as if a certain sequence of bits means, say, “add the contents of register BX to the contents of register AX.” The physical logic of the etched-in circuitry has tiny adding machines, multipliers, logic gates, and the like. Confession of Anxiety in Chapter One Right now, writing this, I feel uneasy. I want The Lifebox, the Seashell, and the Soul to be a fun book, and here I am talking about arithmetic. And now, as if that’s not boring enough, I’ve got to start in on tax forms? Jesus wept. Rap about Halting Being Bad Your experience with pencil-and-paper computations, such as multiplying numbers, may have left you with the impression that a computation has to terminate with an answer. But this need not be true. A computation can be ongoing, with no specific termination time contemplated — think of a flowing river or of a computer screen-saver. Each of the successive states is an output linked to a moment in time. Speaking of time, how long does a computation continue? We won’t impose any bound at all. Certain kinds of computation will indeed signal when they’ve arrived at a desired result ⎯ for instance by beeping or by printing a result ⎯ and then halt in the sense of no longer changing their states. But there’s a sense in which such computational processes continue after their halting point. It’s just that after they halt they remain in a constant state. For a computer that’s supposed to calculate a number halting, is usually viewed as a good thing, but for a living being ⎯ which is also a kind of computation ⎯ halting has the bad connotation of death. Most naturally occurring computational processes are things that we like to keep going as long as possible. Feasibility is Relative Feasibility is relative concept. To say a computation is feasible, you not only need to specify both the hardware and software of the computer system M that you plan to use as well as the amount of time T that you would be willing to wait for an answer. It would be more precise to speak of M-T-feasibility than simply of feasibility. Just to be precise, let’s say that if I speak of feasibility, I’m normally thinking of M as being as good an electronic computer as currently exists on Earth, loaded with the best software algorithms we currently p. 54
Notes for The Lifebox, the Seashell, and the Soul, by Rudy Rucker know of, and being allowed to run for a time T of one year. Barlow and the Web The Web is a big deal. My friend John Perry Barlow, no slouch at self-promotion, used to give talks in which he’d compare the invention of the Web to the invention of fire. And then without flat-out saying so, John would manage to communicate an impression that he’d had something to do with the Web’s creation. Web Wakes Up What if we left all our machines connected and walked away, leaving them to communicate on their own? And what if each machine was itself running some kind of computationally rich program, making its own decisions about when to upload or download information. Might the Web as a whole wake up and start thinking? Game of Life In order to compute a cell’s new value, the Life rule first calculates what we can call the EightSum of the eight nearest neighbors other than the cell itself. And the cell’s own value is looked at separately. The rule for Life can be specified follows: • If the cell’s value is 0 and its EightSum is 3, the cell’s new state is 1. • If the cell’s value is 1 and its EightSum is 2 or 3, the new state is 1. • In all other cases the cell’s new state is 0. Hodgepodge and RainZha The depicted instance of the Hodgepodge rule has a ready state 0, firing states 1 to 31, and a resting state 32. The update rule is as follows: (H1) If the cell is in the ready state 0 compute the sum S of its eight nearest neighbors. If S
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Notes for the Lifebox, the Seashell, and the Soul - Rudy Rucker

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