Texas Instruments TI-81

Date of introduction:  March 1992 Display technology:  LCD dot matrix
New price:  $110 Display size:  8 * 16 characters
Size:  6.8" x 3.1" x 0.85"
 172 x 80 x 21 mm3
Weight:  5.8 ounces, 172 grams Serial No:  1174670
Batteries:  4*AAA + CR1620 Date of manufacture:  mth 11 year 1992 (B)
AC-Adapter:   Origin of manufacture:  Taiwan (I)
Precision:  13 Integrated circuits:  CPU: Toshiba T6A43
 ROM: LH5359©1991
 RAM: LH5160
 Display: 2*T6A39, T6A40
Memories:  0-27    
Program steps:  2400 Bytes Courtesy of:  Joerg Woerner

Texas Instruments entered the market of Graphing calculators in 1990 with the TI-81, a market prepared by the Casio fx-7000G, the world's first Graphing calculator.

While the TI-81 is widely recognized as Texas Instruments' first Graphing calculator, could it be celebrated as the first product of the Equation Operating System (EOS), replacing step by step the revolutionary Algebraic Operating System (AOS) introduced in September 1975 with the SR-52 Programmable calculator.

TI-81_I1192_Back.jpg (235180 Byte)The original design of the TI-81 had a huge disadvantage, it lacked the backup battery for the program and data memory. From a technical point of view replacing the batteries is identical with resetting the whole calculator, clearing all settings, variables, programs etc. Please read the warning in the 1st edition of the TI-81 Graphics Calculator Guidebook.

TI-81_I1192_PCB.jpg (432191 Byte)We assume that Texas Instruments corrected the design early in 1991 and added a small, coin-shaped backup battery. Please notice that even a very early TI-81 Engineering Sample manufactured in April 1990 was prepared for the backup battery but didn't made use of it. Simply by opening the battery compartment on the back of the calculator you recognize immediately what style of TI-81 you talk about.

Dismantling this TI-81 calculator from the second series reveals some surprises: 

The main electronics is centered around a Toshiba T6A43 Application
Specific CPU instead the T6A49(A) found in the first TI-81 calculators.
The display drivers are Toshiba T6A39 resp. T6A40 chips instead the
previous T7778A resp. T7900 chips.

TI-81_I1192_PCBM.jpg (367225 Byte)Most astonishing to us is the find of the Toshiba T6A43 Application Specific CPU in the featured TI-81. We assume that the T6A49(A) had a serious bug and was replaced with the proven T6A43 from the PS-6600 Organizer. Learn more about the Hardware Architecture of TI’s Graphing Calculators. (Comment: The PS-6600 was introduced in 1992, two years after the TI-81.)
[UPDATE]: We located recently a TI-81 w/o battery and the T6A43 chip inside.

Comparing the display boards of different TI-81 models reveals almost identical printed circuit boards (PCBs) populated with either the Toshiba T7778A column drivers and T7900 row drivers or the probably identical T6A39 and T6A40 chips. 

In October 1993 the TI-81 Graphing calculator received a slightly change in its appearance, search the position of the TI-logo here. Please find a detailed overview of the different hardware architectures of the TI-81 generations between 1990 and 1995 here.

Fellow collectors - if you own a TI-81 w/o backup battery  please report us the serial number and date code from the back of the calculator plus the ROM-Version for our TI-81 1st gen Database.

A special "teacher version" called TI-81 VSC combines the standard TI-81 features with a fixed connection to a ViewScreen panel via a flat-ribbon cable. Placing the panel on the overhead projector enlarges the image of the handheld screen so that each student can follow along.

Texas Instruments introduced in 1993 the enhanced TI-82 and in 1995 the low-cost TI-80 leaving not a lot room for the TI-81. Nevertheless did it receive in 1995 another design change before it was discontinued around 1996.

The TI-81 was mentioned in TI's press release dated August 15, 2002 to celebrate the 35th anniversary of its invention of the electronic calculator.

Take a short trip to the TI-78, TI-88 and the Hewlett-Packard HP-41C!

The market of graphing calculators was immediately dominated by Texas Instruments and from time to time we get some figures of the accumulated shipment since the introduction of the TI-81. We noted:

Date of press release Accumulated shipment
Sept. 6, 2000 20,000,000
July 22, 2003 25,000,000



You can check the ROM version of your TI-81 using the following key sequence and reading the number on your screen:

[2nd] [TEST] [ALPHA] [S]

Information provided by and Xavier Andréani.

Exam acceptance:

The TI-81 is permitted (as of September 27, 2007) for use on SAT, ACT, PSAT and AP exams but is not recommended for the AP exam.  

The TI-81 is featured in the Texas Instruments Incorporated sales catalog CL-1233 dated 1994.


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© Joerg Woerner, January 19, 2003. No reprints without written permission.