Texas Instruments Compact Computer 40 (Prototype)

Texas Instruments introduced in January 6, 1983 with the Compact Computer 40 or CC-40 a battery-operated but yet powerful computer based on an 8-bit microcontroller from the TMS7000 family.

The CC-40 Advanced Language Computer (ALC) was a result of the "Project X" initiated already in Summer 1977 and leading to the development of the failed TI Programmable 88 and Compact Computer 70 aka CC-70, too.

The CC-40 can operate about 200 hours with its disposable alkaline batteries and keeps programs and user data even when powered off for several months. It was priced similar to programmable calculators like the TI-59 or TI-88 and continued the idea of Solid State Software Modules with its integrated Cartridge Port.

The CC-40 introduced with the HEX-BUS a very innovative port to connect peripherals in a daisy-chain mode very similar to the USB port released more than a decade later. One of the peripherals planned for the Compact Computer family was the HX-2000 Wafertape, a continuous loop tape drive developed by Exatron and known as Stringy Floppy.

The HX-2000 Wafertape had major reliability issue and was never released to the market. Without any other means for mass storage of programs and data, Texas Instruments developed consequently the Compact Computer 40 Plus with an integrated port to connect a cassette audio recorder to save programs or data files on tape.

Texas Instruments dropped out of the home computer market in March 1984 - after selling more than 2.5 million of the famous TI-99/4A - and production of the CC-40 was ceased immediately after. The CC-40 Plus never made it to the market and only a few prototypes survived.

It took another two years before Texas Instruments introduced with the TI-74 BASICALC and TI-95 PROCALC the successors of both the TI-88 and CC-40. Five different members of the Compact Computer System are known, only two of them where actually released:

The Compact Computer 40 uses the proprietary HEX-BUS to connect peripherals, eight different products like printers, plotters and even a serial interface were available or planned:

The integrated cartridge port of the Compact Computer 40 supports not only pre-programmed Solid State Software Modules like the TI-59, but allows RAM based Memory Expansions and UV EPROM Program Cartridges. Today we know twelve different cartridges but not all of them were released as of March 1984 when the complete Compact Computer portfolio was discontinued:

Please notice that the above mentioned cartridges won't fit with this CC-40 Prototype! Texas Instruments changed the design of the cartridge connector completely between this design stage and the final product. It looks to us like the cartridges were meant to be loaded from top, like the TI-59 and TI-88 Solid State Software Modules, while with the final design of the CC-40 the cartridges are loaded from the rear. We have no explanation why this CC-40 Prototype has 3 rows of 20 contacts, each while the cartridges are using just two rows of zebra connectors.

As of today we know only two Solid State Software Cartridges for the original CC-40 Prototype, they were discovered in Summer 2020 by Brian Green in the Estate of CB Wilson, VP Engineering with Texas Instruments in the 80s:

The bottom shell of the featured Compact Computer 40 Prototype with 2k Bytes internal Memory indicates with its Date code ATA 3982 a manufacturing date during the last week of September 1982 by Texas Instruments in their Abilene, TX facility, contradicting the decision to change the case of the existing ALC (Advanced Language Computer) to accept with different language processors made on September 10, 1982. Dismantling this early Compact Computer 40 Prototype reveals indeed Date codes on two Integrated Circuits (ICs) from October and November 1982. The internal construction of the CC-40 Prototype is based on a efficient design with just two printed circuit boards (PCBs). The Main-PCB illustrates a design with four main building blocks:

CPU (Central processing Unit): The Texas Instruments TMC70C20 microcontroller is a member of the TMS7000 family manufactured in CMOS technology. The original design of the TMS7000 series was introduced in 1981 as an 8-bit extension of the TMS1000 Family to compete with already well established Intel i8051, Motorola M6801, and Zilog Z8 products. The first chips sported 128 bytes of on-chip RAM (Random Access Memory) and either 2k Bytes or 4k Bytes of ROM (Read Only Memory). The featured CC-40 sports with the TMX70C20 with ROM-Code C11002 a very early prototype of the TMC70C20, both equipped with 2k Bytes of ROM. Please notice the Date code 8245 of the TMX70C20, meaning the chip was manufactured about six weeks after the CC-40 Prototype. Read more about TI Standard Symbolization used in the Eighties with ICs manufactured in a metal–oxide–semiconductor (MOS) process. Interesting to observe that the microcontroller of the Compact Computer System CC-40 displays ROM-Code C11002, while the HX-2000 Wafertape sports with ROM-Code L11001.

ROM (Read-Only Memory): The ROM contains the operating system of the calculator or computer. The first products on the market used mask-programmable ROM, the program was stored already during the production of the Integrated Circuit. Later calculators changed to Flash ROM, a technology allowing the programming of the software during the final production stage of the calculator. With the TI-83 Plus and all later graphing calculators from Texas Instruments even the user was able to reprogram the operating system.

The HN61256P ROM of this CC-40 was manufactured by Hitachi in the second week of October 1982 (Date code 2K2) in Japan and offers a capacity of 32k Bytes for the BASIC interpreter. The Texas Instruments part number 1500387-1 suggest software revision 1 while the final CC-40 ROM has a marking 1500387-0003.

RAM (Random Access Memory): The RAM is used as data memory and is used to store both variables, user programs and intermediate results. This CC-40 Prototype makes use of just one HM6116LP manufactured by Hitachi, Japan but sports two empty sockets to accommodate either two additional HM6116LP or two HM6264LP with 2k Bytes resp. 8k Bytes capacity, each. The total capacity of the memory amounts to either 6k Bytes or 18k Bytes with the memory chips installed.

ASIC: The CC-40 uses an AMI 1041036 application-specific integrated circuit (ASIC), it contains the "glue logic" to connect the memories, keyboard and LC-Display to the TMC70C20 microcontroller and integrates the Hex-Bus Peripheral port. With the Hitachi HN61256P used with the CC-40 and its Solid State Software Cartridges featuring a rather long access time of up to 3.5 us and the TMC70C20 CPU lacking a "wait-state" mechanism, incorporates the ASIC additional circuitry to slow down the CPU clock cycle while accessing the ROM chips. The TMC70C46 chip used with the TI-74 BASICALC and TI-95 PROCALC integrated all these features and dropped the additional ASIC found with the CC-40 design completely.

We didn't dismantle this very rare CC-40 Prototype completely and can't provide a view of the second PCB but it uses the same display and keyboard as the final product. Consequently we suspect that it is identical to the PCB documented here.

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

© Joerg Woerner, October 29, 2019. No reprints without written permission.