μblog: engineering from the trenches

Finally had some time to play with Google Code Search. Over all, it is a pretty nifty idea that can allow you to search for some useful things. You can also search public code for profanity. Finally, it is very easy to search for sql database structures that can later be used for sql injection attacks.

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Today I ran across LASI (LAyout System for Individuals), a free generic IC designer that will generate masks that can be sent out to a fab.  With this tool , and  MOSIS, it is theoretically possible to design and implement an IC at a very low cost, if you are in academics that is.  Including a basic tutorial (from U. Colorado) that should help explain some of the cryptic features of the software.

( lasi_inst.pdf ) ( lasi7041b1.zip )

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Richard P. Feynman was once noted for being able to out-perform a mechanical calculator salesman in computation by employing logarithmic arithmetic. The first step to being able to do this effectively is to recognize that a logarithm is a measure of magnitude. With this in mind, we can recognize that multiplication and division of numbers refers to addition and subtraction in logarithm space. The next step is recognizing how to find logarithms without having to carry around logarithm tables. The method that I find useful involves memorizing the logarithm (I chose base 10) of the first ten or so primes, and then factoring the number that I need to operate on into primes in my head.

log(9) = log(3^2) = 2*log(3)

log(0.125) = log(1/8) = log(1/(2^3)) = log(1) – 3*log(2) = -3*log(2)

Once the number is represented as a power of the base, standard logarithmic arithmetic applies and most mathematical operations become pretty easy to do. Finally, converting the result into something useful is a matter of breaking up the result into known inverse logarithms and adding them up in the end. Give this a try next time someone tries to sell you a mechanical calculator, as long as it’s not a Curta.
( exp_and_log_rules.pdf )

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