Texas Instruments TI-88 (DVT)

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:

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

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:

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:

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:

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.

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:

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:

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

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

If you have additions to the above article please email: joerg@datamath.org.

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