Texas Instruments TI-88 (DVT 3)

We wrote May 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 Forth Quarter 1982 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 introduction of the powerful Hewlett-Packard HP-41C calculator or the innovative Sharp PC-1211 Pocket Computer. 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 the decision of a Manager of TI's Consumer Electronic group to quit the calculator business...

Learn more about the demanding "Project X" initiated already in Summer 1977 and leading not only to the (failed) TI Programmable 88, but the TI-66 PROGRAMMABLE, failed TI-76 PROGRAMMABLE, Compact Computer CC 40, (failed Compact Computer CC 70) and last but not least the successful TI-74 BASICALC and TI-95 PROCALC.

As of today we researched almost twenty different TI-88 calculators with twelve different Builds or modifications (learn more about the Five Engineering Stages):

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

Please be aware that the faceplates of most of the surviving TI-88s were updated to the Production Validation Test design and the most reliable indicator of the Three-and a-Half Main Engineering Stages can be found with the Revision Number located on the printed circuit board (PCB):

If you are interested in the subtle differences between the ten 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 MSRPs:

Inside the TI-88

In 2002 the Patent application US4,447,881 filed by Texas Instruments in 1980 was discovered by Juergen Dobrinski and in 2020 a binder labeled "Project X" including schematics of a "TI-85" from the estate of CB Wilson was located by Jon Guidry and made available on his website www.hexbus.com. 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 TI-88 calculator architecture pretty well. The design is centered around a 4-bit microcontroller of the TP0485 family called Master Controller with an associated TP0485 4-bit controller responsible for Timekeeping, Key Scan and I/O functions supported by both ROM (Read Only Memory), RAM (Read/Write Memory) and Display Drivers. We know a similar approach with two controllers already with the TI-55 II.

Dismantling this TI-88 from a DVT 3 (Design Validation Test 3) series manufactured in December 1981 by Texas Instruments in their Abilene, TX facility, reveals a design using the following main components:

The Schematics Diagram from the Patent application of "Product X", leading over "Product 225 TI-85" to the final TI-88 design, omits unfortunately the chip numbers but we could reverse engineer them accordingly.

Learn more about the components used with the TI-88 printed circuit board (PCB) including the Microcomputer Units (MCUs), Customer Read Only Memory (CROM), Customer Random Access Memory (CRAM), and Display.

POWER SUPPLY: We assume that all Integrated Circuits were manufactured in a low-power CMOS 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 and a step-up converter SN77203 to generate both the supply voltage of the Integrated Circuits and LC-Display.

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

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 4 Build reveals two TP0531 Read/Write Memories with 4,800 Bits or 600 Bytes capacity, each 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 with a © 1982 marking from the final TI-88 PVT 4 Build reveals one TP0532 Read Only Memory with Custom Software CD5403 with 120,000 Bits capacity organized as 15,000 Bytes.

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, December 21, 2020. No reprints without written permission.