Calculator Integrated Circuits Forensics

"Calculator forensics" is a term coined by Mike Sebastian which seeks to answer the questions of who originally designed a particular calculator's chip set, what features of a particular calculator have been borrowed from earlier designs, and how has calculator technology spread among the manufacturers. Read more about Mike’s results here. 

Within the Datamath Museum we use the "Calculator forensics" to identify the used calculator chip’s of all featured calculators. Most elder calculators could be opened easily and the chip number identified. However, many calculators cannot be opened without damaging the case or are constructed in such a manner that it is not practical to view the part number. Most modern calculators use „chip-on-board“ designs with the silicon-chip mounted directly on the printed circuit board and a small spot of black resin on top without any part number.

The Forensics Evaluation Algorithm

Observations regarding the embedded algorithms are useful in identifying related calculators. The evaluation algorithm chosen by Mike Sebastian and used in the Datamath Museum is (with the calculator in degrees mode):

arcsin (arccos (arctan (tan (cos (sin (9) ) ) ) ) )

The keystroke sequence (ignoring 2nd, INV, or ARC keys) is typically: 9, sin, cos, tan, arctan, arccos, arcsin. This algorithm usually produces different results on different calculator models (otherwise it would have no value as an evaluation and comparison too.

The following table joins some information together:

• Part number of the chip e.g. TP0324
• Custom numbering of the chip e.g. TP0320 [CD3201]
• Chip family e.g. TMC0520
• Date of introduction of the particular chip
• Number of displayed digits e.g. 10 digits
• Internal accuracy e.g. 13 digits
• Result of the above sequence of trigonometry functions e.g. 9.0000278
• Known calculator models with the particular chip e.g. TI-30 STAT, TI-30 GALAXY

Find a list of all known chips manufactured by Texas Instruments here and the calculator chips manufactured by Toshiba here.