Texas Instruments TI-88 (DVT)

Date of introduction:  Never
 (Announced: May 1982)
Display technology:  LCD dot matrix
New price:  MSRP: $350.00 Display size:  10 (8 + 2)
Size:  6.2" x 3.3" x 1.6"
 157 x 85 x 41 mm3
Weight:  8.3 ounces, 236 grams Serial No:  9-26-81-43
Batteries:  BP88 (1*AA-NiCd) Date of manufacture:  wk 39 year 1981
AC-Adapter:  AC9133 Origin of manufacture:  USA (ATA)
Precision:  13 Integrated circuits:  CD2901, CD2902, CD2903,
 TP531, TP532 (CD5402
Memories:  120-0    
Program steps:  0-960 Courtesy of:  Joerg Woerner
Download product announcement:   (US: 2.1 MByte) Download manual - PREVIEW ONLY:   (US: 4.2 MByte)

We wrote the year 1982 when Texas Instruments printed the sales brochures of the TI-88 on glossy paper. The brochures promised the introduction of the TI-58C/TI-59 successor for 1983 in a package matching the TI-55-II line - before we got word of the TI-66. Today we know more: The development of the TI-88 was finalized, the manuals printed, the first pre-production calculators worked perfectly and Texas Instruments canceled the whole project! Maybe one of the reasons was the powerful Hewlett-Packard HP-41C calculator. Or the underestimated complexity of the TI-88 design. Or electrostatic discharge (ESD) issues of the Module contacts. Or the internal competition with the CC 40 Compact Computer. Or the keyboard problems encountered with the TI-55-II family of calculators. Or...

Currently we know ten TI-88 from five different builds (learn more about the Five Engineering Stages) that survived:

Owner Serial Number Build: Date of Manufacture
Joerg Woerner 9-26-81-43 Design Validation Test ATA wk 39 year 1981
Heinz Nixdorf Forum t.b.d. Design Validation Test t.b.d.
Joao Oliveira NTC-3-4-30-82 Engineering Validation Test ATA wk 17 year 1982
Joerg Woerner 000337 Production Validation Test 1 ATA wk 21 year 1982
Marie Lisa Collas 000341 Production Validation Test 1 ATA wk 21 year 1982
Viktor T. Toth 001101 Production Validation Test 2 ATA wk 32 year 1982
Joerg Woerner 002023 Production Validation Test 3 ATA wk 33 year 1982
Luis Gómez 002055 Production Validation Test 3 ATA wk 33 year 1982
Monty McGraw 002069 Production Validation Test 3 ATA wk 33 year 1982
Smithsonian Institute 002074 Production Validation Test 3 ATA wk 33 year 1982

Just looking at the keyboard of the TI-88, you can easily differentiate between the three Engineering Stages identified so far:

[ALPH] Key [R/S] Key Build: Notes
Design Validation Test Grey [ALPH] key
No dot next to [R/S] key
Engineering Validation Test Red [ALPH] key
No dot next to [R/S] key
Production Validation Test Red [ALPH] key
Red dot next to [R/S] key

If you are interested in the subtle differences between the five different builds discovered as of today, please follow this link.

Compared with the TI-58C you'll notice some differences and similarities:

The display is alphanumeric and prompts system messages in readable English.
The Constant Memory™ covers program and user memory.
The Solid State Software™ concept allows the expansion of two cartridges, either application programs (CROM) or user memory (CRAM).
Beside the traditional key-stroke programming, a formula mode is available.
A real time clock adds time and date.
A small speaker generates sounds. 
A printer port accepts the PC-800 printer.
A Cassette Interface CA-800 allows the permanent storage of both programs and data with a tape recorder.

It is a pity that the TI-88 with the perfect prompting system never made it to the market. The next calculators in the "Programmable/Scientific line" are the TI-95 PROCALC and the first Graphing calculator TI-81.

A Texas Instruments price list printed in July 1982 suggested these MSRP's:

Product MSRP (July 1982)

TI-88 Programmable Calculator


PC-800 Printer


CA-800 Cassette Interface


Constant Memory Modules CRAM


Solid State Software Modules CROM


Inside the TI-88

Recently the Patent application US4447881 filed by Texas Instruments in the year 1980 was discovered by Juergen Dobrinski. Together with hours and hours of reverse engineering based on the inside views of the five different TI-88 builds discovered so far and looking into various CRAM and CROM Modules, we understand the calculator architecture pretty well. The design is centered around a 4-bit microcontroller of the TP0485 family called Master Controller with two associated TP0485 4-bit controllers responsible for the Arithmetic and the I/O supported by both ROM (Read Only Memory) and RAM (Read/Write Memory). We know a similar approach with two controllers already with the TI-55 II.

Dismantling this TI-88 from the final PVT 3 (Production Validation Test 3) series manufactured in August 1982 by Texas Instruments in their Abilene, TX facility, reveals a design using the following main components:

CD2901 (TP0485) Timekeeping, Key Scan and I/O Controller 
CD2902 (TP0485) Master Controller 
CD2903 (TP0485) Arithmetic Controller 
CD5402 (TP532) On-board Read Only Memory
TP531 On-board Read/Write Memory
Plug-in Memories which may be either Read Only Memory or Read/Write Memory
Cascadable Display Drivers 
SN77203 Display Interface Voltage Controller Chip

The Schematics Diagram from the Patent application omits unfortunately the chip numbers but we could reverse engineer them accordingly.

We assume that all Integrated Circuits were manufactured in a low-power C-MOS process, nevertheless used Texas Instruments once again a rechargeable battery pack. Instead of the 3 AA-sized NiCd cells of the TI-59 introduced in 1977, used this design of 1982 just one AA-sized cell. 

Running Mike Sebastian's "Calculator forensics"  gives a result of 9.000000955917. It took 7 years before with the TI-68 another Texas Instruments calculator achieved a similar precision.

CRAM and CROM Modules

The TI-88 accommodates up to two modules in the rear slots. 
Two different type of modules were designed:

CRAM-Modules as user programmable memory with either 1184 program steps or 148 user memories.

With 0, 1 or 2 CRAM-Modules you get a total of:

CRAM-Modules Default Max. Program steps Max. User memory
  Program steps User memory Program steps User memory Program steps User memory
0 480 60 960 0 0 120
1 480 208 2144 0 0 268
2 480 356 3328 0 0 416

Dismantling a CRAM-Module from the final TI-88 PVT 3 Build reveals two TP531 Read/Write Memories with unknown capacity and a Sanyo 3 Volts lithium battery with 24.5 mm diameter and a thickness of 3.5 mm - matching today's CR2430 cells.

  CROM-Modules as pre-programmed software like the earlier TI-58C/TI-59 Solid State Software™ modules with up to 15,000 program steps.
   Eight modules were already defined in the sales brochures:

CROM-Module Content
1 Master Library
2 Statistics Library
3 Electrical Engineering Library
4 Finance Library
5 Surveying Library
6 Mathematics Library
7 PGM Development Library
8 Chemical Engineering Library

Dismantling a Master Library CROM-Module from the final TI-88 PVT 3 Build reveals one TP532 Read Only Memory with Custom Software CD5403 with unknown capacity.

Heinz Nixdorf MuseumsForum (HNF)

The MuseumsForum is dedicated to Heinz Nixdorf, the computer pioneer, founder of Nixdorf Computer AG and successful entrepreneur with a vision for the future of information technology and a sense of social responsibility for his staff, who died in 1986. He firmly believed that computers could help people to fashion a better future for themselves.

Out of this conviction was born the idea of making the history of the computer’s development accessible to the general public in a museum. He himself laid the foundations for this project with his collection of over 1,000 objects in the field of office communications. His Stiftung Westfalen foundation took up the baton after his death, extending his collection in line with contemporary developments and giving it a home in the Heinz Nixdorf MuseumsForum. Fellow collector Olivier Dumas provided us a picture of their TI-88 and it is clearly a "Design Validation Test" Build with a red [2nd] key.

Lucky Numbers?

People in China traditionally associate luck with numbers. As a rule in day-to-day life in China, it is customary to regard even numbers as being more auspicious than odd numbers. Eight, 'Ba' in Chinese has a similar sound to 'Fa', which means to make a fortune. All business men favor this number very much. However, for Texas Instruments the "8" in the type designation was not always a fortune.

We remember some very unlucky calculators:

Calculator Introduction
TI-18 1982 A BASIC calculator with a SCIENTIFIC appeal
TI-38 1979 The odd sibling of the TI-50 and TI-53
TI-68 1989 How NOT to do a keyboard layout
TI-78 1990 Too late? Too advanced? Who knows... 
TI-88 (1982) Killed by competition?
TI-98 (2002) Just a fantasy number, but it would fit.

History repeats - don't miss the story about the PET Project!

The TI-88 is featured in the Texas Instruments Announcement dated May 1982.

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If you have additions to the above article please email:

© Joerg Woerner, October 10, 2019. No reprints without written permission.