Texas Instruments TI-81

Date of introduction:  May 1990 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:  0935021
Batteries:  4*AAA Date of manufacture:  mth 09 year 1990
AC-Adapter:   Origin of manufacture:  Taiwan (I)
Precision:  13 Integrated circuits:  CPU: Toshiba T6A49A
 ROM: ©1990
 RAM: TC5565A
 Display: 2*Toshiba T7778A, T7900
Memories:  0-27    
Program steps:  2,400 Bytes Courtesy of:  Joerg Woerner

With the famous TI-81 Texas Instruments entered the market of Graphing calculators. Instead of the traditional 1-line display this kind of calculator offers a dot matrix display with 64 * 96 addressable pixels. In the normal calculator mode up to 8 lines of text information are shown. The TI-81 traces back to the Casio fx-7000G, the world's first Graphing calculator.

The main features of the TI-81 in a short summary:

Graphing of up to 4 functions at one time.
Parametric graphing to analyze up to three parametric equations.
Manipulation of three matrices with dimensions of 6*6.
One- and two-variable statistical analyses with up to 150 data points.
Up to 37 programs with a total of 2,400 Bytes.

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.

Please notice that this TI-81 from an early manufacturing series lacks a backup battery. The TI-81, like all Texas Instruments graphing calculators including even the latest TI-84 Plus Silver Edition, store the user program, user data and even calculator and display settings in a volatile C-MOS memory. To avoid the lost of the memory while replacing the main batteries, the mentioned calculators use an additional, coin-shaped, backup battery. Please read the warning in the 1st edition of the TI-81 Graphics Calculator Guidebook.

The TI-Nspire, introduced July 2007, was Texas Instruments' first graphing calculator using non-volatile Flash memory to maintain the information stored in the calculator even with low or empty main batteries. 

From a technical aspect the TI-81 combines the 8-bit Hardware Architecture known from the Financial Investment Analyst FIA-10 and the enhanced capabilities from the TI-95 Procalc. Learn more about the Hardware Architecture of TI’s Graphing Calculators.

The hardware of the TI-81 is similar to a lot of other products: An 8-bit microprocessor of the Z80 family, a huge ROM of 128k Bytes capacity, a Static RAM (SRAM) of 8k Bytes size and a driver for the LCD display. You'll find similar architectures with just another balance of RAM and ROM capacity:

Product ROM-size RAM-size Example
Spell-Checker 128k Bytes 2k Bytes RR-1
Data Bank 64k Bytes 64k Bytes PS-6700
Graphing calculator 64k Bytes 8k Bytes TI-81
Modern graphing calc 512k Bytes 32k Bytes TI-83 Plus

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

The main electronics is centered around a Toshiba T6A49A Application
Specific CPU instead the T6A43 found in the final TI-81 calculators.
The display drivers are Toshiba T7778A resp. T7900 chips instead the
later T6A39 resp. T6A40 chips.
We miss indeed the backup battery but the mounting space is obviously

Most astonishing to us is the find of the Toshiba T6A49A Application Specific CPU in this early TI-81, the common version with backup battery uses a T6A43 chip. We assume that the T6A49A had a serious bug and was replaced with the proven T6A43 from the PS-6600 Organizer. (Comment: The PS-6600 was introduced in 1992, two years after the TI-81.)

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. 

Late in 1991 the internal construction of the TI-81 was revised and missing backup battery was added. 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.

Don't miss a rare TI-81 Engineering Sample, manufactured probably in April 1990. 

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.

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.  


Find here the original press release dated September 6, 2000:

Texas Instruments celebrates shipping more than 20 million graphing calculators

DALLAS, September 6, 2000

Texas Instruments, leaders in classroom technology, announced today that they have shipped more than 20 million graphing calculators with this Back-to-School season. Since entering the graphing calculator market in 1990, TI has consistently led the graphing calculator segment and experienced firsthand, the growing trend of classroom technology.

While computers are increasingly used in schools, graphing calculators are the most pervasive form of technology in student's hands across the United States . Graphing calculator sales have been averaging about 10 percent growth for the last several years and are rapidly gaining favor in other countries.

"We're constantly hearing people tell us that they used our products in high school." said Tom Ferrio, vice president, Texas Instruments, "They're always amazed at the power and capabilities that the tools now have."

Graphing technology has changed dramatically since TI first introduced the TI-81 in 1990. Products now boast operating systems that can be electronically upgraded via the Internet, calculator software applications (Apps) for adding specific functionality, and peripherals for data collection and real-world experimentation.

"I've used graphing technology in my classroom for five years," said Melissa Rowe, math teacher, South Grand Prairie High School. "The advancements in the tools have helped my students advance deeper into the math and master more complex subject matter than ever before."

In the last decade, TI has introduced 11 graphing technology products, many of them improved versions of their predecessors. The current product family includes the most popular graphing product in the United States, the TI-83 Plus, for high school and college math and science; the TI-73 for middle grade students; and the TI-89 and TI-92 Plus for advanced mathematics through college and graduate studies.

Over 30 software Apps are available for the above products, with many available to schools and students free. Some Apps even provide actual curriculum in electronic format that compliments classroom textbooks.

To celebrate it's 10th Back-To-School season, TI is offering four TI-83 Plus Apps free with product purchase for a limited time. (More information at


TI-81 Graphics Calculator Guidebook

TI-81 Graphics Calculator GUIDEBOOK 

Copyright © 1990 by Texas Instruments Corporated.

B-2: Effects of Replacing the Batteries

The calculator cannot hold data in its memory when the batteries are removed or become discharged. Replacing the batteries has the same effect as resetting the calculator.

1-28: Resetting the TI-81

Resetting the TI-81 restores the memory to the factory settings. Because there are operations that clear only selected portions of memory, the TI-81 should be reset only under special circumstances, such as when it is first acquired.

1-28: Results of Resetting

When you reset the TI-81:

The contrast setting is set to 7.
The MODE settings are set to the defaults.
The viewing rectangle is set to the standard defaults.
All variable values are set to zero.
All statistical data is erased.
All matrix values are set to zero.
All matrix dimensions are set to 6 by 6.
All functions in the Y= list are erased.
All programs are erased.
Zoom factors are set to 4.
Rand is reset to the factory seed of 0.


TI-81 1st gen Database

Serial Number Date code ASIC ASIC code ROM-
none none Toshiba T6A49 9018 1.0 Joerg Woerner
1013019 I-1090 Toshiba T6A49 --- 1.0 Conrad
0500937 I-0590 --- --- 1.0 Eric Mumpower
0712731 I-0790 --- --- 1.1 Rick Skrbina
0801262 I-0890 Toshiba T6A49A 9030 1.1 Jeff Delhaye
0935021 I-0990 Toshiba T6A49A 9030 1.1K Joerg Woerner
--- I-1090 --- --- 1.1K Xavier Andréani
1018059 I-1090 --- --- 1.1K Scott
1107787 I-1190 Toshiba T6A49A 9037 1.1K Marc Ferrer
1208166 I-1290 --- --- 1.1K Jim Kelly
--- I-1290 --- --- 1.1K Xavier Andréani
0207888 I-0291 --- --- 1.1K Xavier Andréani

I-0391 Toshiba T6A43 --- 1.5K Jérôme Quartanar
Charlie Leemburg
0519319 I-0591 Toshiba T6A43 --- 1.6K John Meine
0615087 I-0691 Toshiba T6A43 --- 1.6K Bas Bekema
0748924 I-0791 Toshiba T6A43 --- 1.6K Bob Vargo
0829623 I-0891 Toshiba T6A43 --- 1.6K Radboud Hack
0917651 I-0991 Toshiba T6A43 9118 1.6K Joerg Woerner
1239636 I-1291 Toshiba T6A43 9145 1.6K David Petty
0178640 I-0192 Toshiba T6A43 --- 1.6K K.G.S. Simmons

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