Texas Instruments TI-66 PROGRAMMABLE    

Date of introduction:  May 1983
 Available: August 1983
Display technology:  14-segment LCD
New price:  $69.95 (SRP 1983)
 DM 112.65 (UVP 1983)
Display size:  10 (8 + 2)
Size:  3.4" x 5.7" x 0.6"
 86 x 145 x 15 mm3
Weight:  3.7 ounces, 105 grams Serial No:  296531
Batteries:  2*LR44 Date of manufacture:  mth 07 year 1984
AC-Adapter:   Origin of manufacture:  Japan
Precision:  13 Integrated circuits:  Toshiba T6875(A), TC5514A
Memories:  0-64    
Program steps:  512-0 Courtesy of:  Joerg Woerner
Download leaflet:   (US: 0.7M Bytes) Download manuals:    (US: 12.7M Bytes)
(US: 11.5M Bytes)
(US: 4.5M Bytes)

TI-66_BACK.jpg (294079 Byte)Texas Instruments introduced the TI-66 Programmable in 1983 as successor of the legendary TI-58 and TI-59 calculators. The TI-66 Programmable compares best with the TI-58C, the latest member of the TI-58 family manufactured between 1979 and its discontinuation in 1983. 

  TI-58C TI-66
Introduction 1979 1983
Weight 8.5 ounces, 240 grams 3.7 ounces, 105 grams
Precision 13 digits 13 digits
Batteries 3 * AA NiCd 2 * LR44
Display size 10 (8 + 2) LED 10 (8 + 2) LCD
Memories 0 - 60 0 - 64
Program steps 480 - 0 512 - 0
Printer PC-100C PC-200

The TI-66 Programmable was the first Texas Instruments calculator in landscape orientation, probably inspired by Hewlett Packard's very successful "Voyager" series (HP-10C, HP-11C, HP-12C, HP-15C, and HP-16C) of programmable calculators introduced in 1981. The next design iteration of the TI-66 Programmable led to both the TI-30 Galaxy in 1984 and TI-62 Galaxy in 1986.

TI-66_PCB.jpg (633709 Byte)Dismantling the featured calculator manufactured in July 1984 in Japan reveals two surprises! The whole electronics of the TI-66 Programmable was squeezed into just two chips labeled Toshiba T6875 resp. Toshiba TC5514A and the printed circuit board (PCB) shows a very prominent Toshiba logo.

TI-66_CPU.jpg (141302 Byte)The partitioning of the two Integrated Circuits is rather obvious, the Toshiba T6875 is a 4-bit Microcomputer with internal ROM (Read-Only Memory), integrated display driver, keyboard scanning logic and interface to an external RAM (Random Access Memory) circuit. The ROM is used for the calculator "operating system" and constants, while the RAM stores both the user program and user data. We know TI-66 Programmable calculators with later manufacturing dates sporting a T6875A chip, instead. The switch happened in Summer 1984, known T6875 date codes are till April 1984 and known T6875A date codes are after August 1984 and at least till July 1986. Thanks, Brian!

TI-66_RAM.jpg (147921 Byte)The featured TI-66 Programmable manufactured in July 1984 makes use of a TC5514A manufactured by Toshiba, Japan. The capacity of the memory is 1k * 4 bits.

A nice feature of the calculator is the connectivity to the serial printer PC-200 known from the financial calculator BA-55

Don't miss the talking Calcu-Talk based on the TI-66.

If you are interested in the calculating accuracy of scientific calculators don't miss the Calculator forensics.

Read more about the calculators developed, manufactured and / or sold by Toshiba.

The TI-66 Programmable is featured in the Texas Instruments Incorporated bulletin CL-837E dated 1985.

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If you have additions to the above article please email:

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