DATAMATH CALCULATOR MUSEUM
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DATAMATH CALCULATOR MUSEUM |
Texas Instruments TI-81 (Engineering Sample)
| 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 |
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| Weight: | 5.8 ounces, 172 grams | Serial No: | |
| Batteries: | 4*AAA | Date of manufacture: | mth 04 year 1990 |
| AC-Adapter: | Origin of manufacture: | Taiwan | |
| Precision: | 13 | Integrated circuits: | CPU: Toshiba T6A49 ROM: ©1990 RAM: TC5565A Display: 2*Toshiba T7778A, T7900 |
| Memories: | 0-27 | ||
| Program steps: | 2,400 Bytes | Courtesy of: | Joerg Woerner |
Some
weeks ago, mid of December 2008, Marc Ferrer, a fellow calculator collector
living in France, reported an amazing find: A very early TI-81 - manufactured in
November 1990 - lacking the 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. 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.
We started immediately a research and contacted dozens of
TI-81 sellers and buyers on eBay with three questions about the backup battery,
serial number and manufacturing code. Within
three weeks a seller from Upstate New York reported a TI-81
manufactured in September 1990 lacking the space for the battery with the serial
number 093521. Another week later an email from Oregon: Sorry, no serial number,
no manufacturing code and no space for a coin-shaped battery. Bingo!
Dismantling
the calculator reveals some surprises:
| • The main electronics is centered around a Toshiba
T6A49
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 available. • All Integrated Circuits are manufactured on or before May 1990, long before the official introduction of the TI-81. |
We assume that the featured TI-81 is a rare Engineering Sample that leaked to the market or was used for first acceptance tests at different schools.
Most
astonishing to us is the find of the Toshiba T6A49 Application Specific CPU in
this early TI-81, the "final" version w/o backup battery manufactured
in September 1990 uses a revised T6A49A chip while the common version with
backup battery uses a T6A43 chip. We assume that the T6A49(A) 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. Please find a detailed overview of the different hardware architectures
of the TI-81 generations between 1990 and 1995 here. Learn more about the
Hardware Architecture of TI’s Graphing Calculators.
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.
ROM-Versions:
1.0
You can check the ROM version of your TI-81 using the following key sequence and reading the number on your screen:
