Texas Instruments TI-81

Date of introduction:  October 1993 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:  5.6 ounces, 168 grams Serial No:  20023247
Batteries:  4*AAA + CR1620 Date of manufacture:  mth 08 year 1994 (F)
AC-Adapter:   Origin of manufacture:  Taiwan (I)
Precision:  13 Integrated circuits:  CPU: Toshiba T84C00
 ASIC: Toshiba TC14L010
 ROM: LH5359©1993
 RAM: SRM2264 
 Display: T6A04
Memories:  0-27    
Program steps:  2400 Bytes Courtesy of:  Joerg Woerner

TI-81_I0894F_Back.jpg (267776 Byte)Texas Instruments changed in 1993, together with the introduction of the TI-82, the design of the TI-81 slightly. Please notice the position of the TI-logo, it moved from the upper right position to the upper left of the screen.

From much higher interest to us are the design changes inside the third series of the TI-81. Dismantling this calculator manufactured in February 1994 reveals two major changes:

The three display drivers (two T6A39 column drivers and one T6A40 row drivers) housed in huge Quad-Flat-Pack packages of the original design were replaced by one tiny Toshiba T6A04 chip directly attached to the flexible printed circuit board (Flex-PCB) of the LCD display.

Even the main printed circuit board (PCB) was changed completely and looks identical to the PCB found in the TI-82. Instead the Toshiba T6A43 - an application specific Z80 controller - it accommodates now with the Toshiba T84C00 a standard Z80 CPU with an additional ASIC Toshiba TC14L010 (1.0 micron C-MOS gate array with 1,000 usable gates). 

We recently learned that the major changes in the hardware design are not correlated with the cosmetical changes. A fellow collector noticed identical hardware in a TI-81 sporting the old design and manufactured in September 1993.

Texas Instruments changed in 1995 the design of the TI-81, TI-82 and TI-85 slightly, please notice the position of the TI-logo and the color of the type designator. Please find a detailed overview of the different hardware architectures of the TI-81 generations between 1990 and 1995 here.




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.  


horizontal rule

If you have additions to the above article please email:

© Joerg Woerner, December 5, 2001. No reprints without written permission.