Floating Point Processor found after 15 years!

by Carsten Thomsen

Yes, it’s the slide rule, a basic tool for engineering for many years before the days of electronic calculators.

When I visited Dr. T in July 2021, he showed me his slide rule which had powered him though his engineering and physics studies. Unfortunately, it had disappeared, but was returned after being lost for 15 years.

Before you think it is a tool that belongs to the dinosaurs, consider this:

  • It computes all results and displays them in parallel. For example, if you multiply by pi, it shows all results in parallel. It’s a sliding look-up table with about 3 digits accuracy. Today, in the days of high performance GPUs and neural networks, all of these have massive parallel multipliers…something the slide rule also does automatically for all visible numbers.
  • But you have to manually figure out where to put the decimal point (or exponent of 10). This requires development of good “order of magnitude skills” and demanded that good estimation skills. Unfortunately this skill has been lost by many engineers, who today use calculators or just key the expression into the Google search.
  • Frequent use of slide rules also helps development of good mental math skills…a competitive advantage of being able to rapidly estimate and compare numbers, ratios, percentages etc.
  • And the slide rule has a non-volatile memory!

If you don’t know how to use a slide rule, look at this YouTube Video.

How to use a Slide Rule

Digging around in my drawers, I found several special purpose engineering slide rules!

Just imagine how many engineering problems have been solved by these!

And it went to the moon…  (thanks to Nick Velychko for sharing)

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And to illustrate “numerical blindness” just note the screen shot of an article posted five days ago, i.e. Sept 22. Really depressing news 😉

Share photos of your slide rules! Just add them as attachments to your comments and tell what you used them for!


One reply on “Floating Point Processor found after 15 years!”

The slide rule is a mechanical analog computer (wikipedia). As a graphical analog calculator, the slide rule is closely related to a nomogram.

It is used primarily for multiplication and division, and also for functions such as exponents, roots, logarithms, and trigonometry, and typically not for addition or subtraction.

In “advanced mode” a slide rule is used as Complex Numbers Calculator. In fact, there are often more imaginary numbers in electrical engineering problems than there are real numbers.

By design, slide rule is one of the 1st graphical user interface (GUI) widely used in LabVIEW.

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