The Logic Behind Pre AOS TI Calcs

[Matt Agajanian]

Hello all.

As I remember from browsing the brochures for TI's SR-50 and 51 (thanks Joerg Woerner), it was mentioned at the last pages of the brochures that TI had a choice between algebraic and RPN entry (which featured a somewhat inaccurate representation of RPN's method to solving the example). But, alas, and here's a lead in to the point of my curiosity, neither the original SR-50, SR-51, nor their A versions featured parentheses but, incorporated an x<>y exchange mechanism. More to the point, in the manuals for these four calcs, the keystroke sequences for the more advanced calculation examples were far from straightforward entry methods.

So, my question or questions are in what ways were TI's entry methods for the SR-50, 51, 50A, 51A natural and easier (or even easier than RPN, for that matter)?

[Steve Simpkin]

(04-12-2014 02:16 AM)Matt Agajanian Wrote:  So, my question or questions are in what ways were TI's entry methods for the SR-50, 51, 50A, 51A natural and easier (or even easier than RPN, for that matter)?

I certainly don't think these early models without parenthesis keys were easy to use on complex calculations. The mental gyrations needed for calculating parenthesis heavy formulas could be daunting if you didn't break down the equation into simpler subsets first. Even then, this may have required intermediate results to be written down and re-entered in order to solve some problems.

I have always thought that the reason they didn't implement parenthesis keys on these early models was because of transistor count. It takes approximately 4-6 MOS transistors to provide a bit of storage in these IC designs. If a register occupies about 56 bits (as in the early HP models) then that translates into approximately 200-300 transistors per register. The early MOS LSI IC designs in this era were often limited to around of 2000-6000 transistors per IC. The "cost" of adding 5-7 extra registers needed for a good parenthesis implementation on top of the existing working registers was probably just too great for these early TI models.

Conversly, HP models, with their RPN logic and a four level stack, were able to provide a workable entry system that allowed most problems to be solved without writing down intermittent results. The methods used to break down a problem and to work it from the inside out also had the added advantage of mimicking the methods you would have used to solve the problem with a pencil and paper (or a slide rule).

Just my opinion.

[Matt Agajanian]

Well, last night, as I was investigating through the SR-51/51A manual (Thanks Jorge), I was in a maze of overwhelmed at the maze of keystroke gymnastics, the overt need to use the equals key to compute and store intermediate results. Another nuance I took note of was how the equations' entries needed to be rearranged. Yes, rearranged. So yes, while I most definitely concur, TI's pre-AOS logic was far, far away from any sense of natural entry method, RPN has always maintained a consistently natural logic system.