DATAMATH  CALCULATOR  MUSEUM

Montgomery Ward P8M aka TXI-8646A

Date of introduction:  August 20, 1973 Display technology:  LED-modules + lens
New price:  $99.50 Display size:  8
Size:  5.7" x 3.1" x 1.6"
 146 x 79 x 41 mm3
   
Weight:  5.1 ounces, 144 grams Serial No:  47F-0023467
Batteries:  4*AA Date of manufacture:  wk 20 year 1974
AC-Adapter:   Origin of manufacture:  USA
Precision:   Integrated circuits:  WD LC1552B
Memories:  1    
Program steps:   Courtesy of:  David Smith

TXI-8646A_Back.jpg (240362 Byte)This neat calculator does not look like a Texas Instruments product. To identify it, you have to know more about the coding used by Montgomery Ward:

Models starting with

TXI were produced by Texas Instruments
DAN were produced by APF
DNS were produced by National Semiconductors (later Novus)
GLE by Lloyd's

If you remember the famous Texas Instruments Datamath (TI-2500) and add a 4-key memory you would get a similar calculator to this wonderful find. There are only few calculators reported which have no direct counterpart of existing TI-products. With the P8F alias TXI-8644A and the P8P alias TXI-8645A two similar calculator without memory were sold, too.

TXI-8646A_PCB.jpg (35129 Byte)If you dismantle this calculator, one question will arise immediately:
Was this calculator really manufactured by Texas Instruments?


 
TXI-8646A_IC.jpg (13842 Byte)The integrated circuit inside is not manufactured by Texas Instruments and one step ahead the TI chips of that era. The TI-2550 with similar complexity (%-key and 4-key memory) was introduced almost 6 month later. Maybe TI had a delay in the development of the TMS0601, the direct counterpart of the Western Digital LC1552 used with this P8M. 

The keyboard of the calculator is a mixture of the TI-1500 keys and the grid of the Datamath. The display board was manufactured by Texas Instruments, too. And we could proof easily: This cutie IS a Texas Instruments calculator. The answer is found in the magic number 13-04-709-478 on the printed circuit board. Read more here. With the Radio Shack EC-300 Texas Instruments used the LC1552 a second time.

Don't miss the rare TXI-8661A based on the Exactra 23 calculator.

Datamath™ is a trademark of Texas Instruments.

horizontal rule

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

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