The Texas Instruments TI-74 BASICALC and TI-95 PROCALC

After TI discontinued the CC-40 and scrapped the CC-40+ project in 1984, people wondered why?  After all, the 40+ was just about ready to roll.  The next year we found out why.  Seems Texas Instruments had been working on a cost reduced and size reduced version, the TI-74 BASICALC.

Starting at 8K, instead of the CC-40's 6K, the 74 has a little more capability.  An 8K RAM cartridge was available for additional memory.  The 8K cartridge, being battery backed, allowed you to keep a program stored there for immediate access or you could swap the contents of the cartridge with the contents in main memory!

BASIC in the 74 was very close to both the 99/4A's  Extended BASIC and CC-40's BASIC.  Obviously, some of the display commands won't work!  Of course, they don't work in the CC-40 either!

Another nice thing is the batteries were reduced from 4 AA's to 4 AAA's.  Again, reducing the weight, but not affecting the performance.  Battery life isn't rated by TI, but 30-50 hours of use isn't uncommon.

Something else that is useful is the MODE key.  Pressing it will transform the 74 from a pocket computer into a very powerful scientific calculator with 70 built in functions.

One major shortcoming of the CC-40 was a lack of anyway to store a program in anything other than RAM.  The 74 addressed this shortcoming with a cassette interface.  Just plug it into the Dockbus, hook up a cassette recorder and enter the appropriate command and now you don't have to worry about the batteries dying on you.  Program is safe and snug on the cassette!

TI took this a step further and developed the PC Interface, aka PCIF.  By hooking this up to your computer's parallel port, you not only could use the computer's drives (both hard and floppy) for storage, but you could also use the monitor for display purposes!  The PCIF effectively allowed you to display a full screen!  Definitely an improvement over the CC-40 here!  Since Texas Instruments is no longer manufacturing the PCIF, several people have reverse engineered the interface and doped out the circuitry.  If you want to build your own, here's the diagram.

A bit of a problem with the PCIF involved its driver software for the computer.  It had a problem with bottlenecks on faster computers and couldn't keep up.  Peter Engels in Germany has developed a newer version that is fully customizable for faster processors.  He's named his program TIIF.  It's currently up to version 3.12.  No documentation is provided, but with pull down menus, autodetect of PCIF connection and built-in text editors for b74 files, do you really need the documentation?  You can get a copy here.  The bad news is it's a DOS only program.  He has also developed a version for OS/2 and if you want a copy of it, you'll have to drop him a line.  Unfortunately, his web site is in German.  However, Babel Fish works pretty good!

While introduced in 1985, the 74 was still being sold in 1992!  Quite a run for a machine whose predecessor was killed after only a couple of years.  Part of this may have been due to TI's aggressively marketing the 74 in the OEM segment.  A version of the 74 was released called the TI-74S.  The major difference was the keyboard.  None of the special functions were shown on the keyboard.  It looked like your generic alpha-numeric keyboard.  The kicker was that all the functions are still there, you just have to know how to find them.  Usually, the 74S was provided with a custom cartridge that dominated the computer and would only run its built-in program.  However, if you were to take out the cartridge, it became a standard 74!

I met a fellow who was involved with both the CC-40 and TI-74 projects.  His name is Stephen Reid.  A long-time employee of Texas Instruments, he is quite an interesting and accomplished fellow.  Here's the link to his webpage.  Drop him a line and tell him I said hi!

The TI-95 PROCALC was released in 1986 and was aimed at more professional and traditional calculator programmers.  While it could be programmed in the built-in BASIC, it could also be programmed step style.  TI seems to have directed the 95 as a competitor to the HP 41C.

Expansion is still done via either the cartridge port or a new buss called the Dockbus.  While looking entirely different, in fact electrically, the Dockbus and Hexbus are really one and the same!  It took some digging, but I have managed to create a portable interface between the 2.  Now I can use the PCIF on my CC-40 to store programs and display full screens of information, not just a single line!  Or, you can use hexbus peripherals on the 74 and 95!  Much better!!!  If you're interested in doing the same thing, check below for more details and pictures.

The TI-74 and 74S.  The 74 is the lower unit and you can see the keyboard is a LOT busier!

The 74S keyboard.  Nothing but the basics (pardon the pun).

TI-95  You can tell it's designed for an entirely different audience.

The peripherals available for the 74 and 95 AND the CC-40 with the use of my adapter!

Here's what my adapter looks like closed up.  Since all dockbus cables are attached a dockbus cable isn't needed.  As you can tell, there's room in the adapter for a short hexbus cable.  And yes, the case is nothing more than an old TRAVAN tape.


The bottom of my adapter.  Since the battery isn't needed all the time, I installed an on/off switch for them.

What the dockbus plug looks like.

The hexbus plug.  Note:  I cut these out with an exacto knife and was trying to NOT slice my finger again.  I've since found a square punch at a scrapbooking supply shop and will attempt to remake the holes.

What it looks like from the top.  Nice and neat with only a few wires.  You can also get an idea of the size by the ruler in the background and the fact the power pack is 4 AAA batteries.

The bottom side of the circuit.  A little messier due to the soldering.  Notice the positioning of ground and positive voltage input.  Drove me nuts getting that sorted out!

So, you want to build your own interface, eh?  Okay.  Here's the information you'll need.  I've found Jameco to be a good source for the pins.  
The circuit board can be had at Radio Shack.    Ditto the wire.  I used wirewrap wire.  As far as a case, you're on your own there.  


Dockbus Interface

Hexbus Interface
 4  3  2  1
_____________|      |_____________
|  o  o  o  o  o  o  o  o  o  o  |
   1  2  3  4  5  6  7  8  9  10   
_____|  |_____
| o  o  o  o |
| o  o  o  o |
  8  7  6  5


System power distribution - output
PO 1*    
System power distribution - input PI  2*    
Data bit - least significant bit D0 3 D0 Data-LSB 1
Data bit D1 D1 Data 2
Data bit D2 5 D2 Data 7
Data bit - most significant bit D3 6 D3 Data-MSB 8
Handshake - I/O timing control line HSK 7 HSK           5
Bus Available - I/O Traffic control line BAV  8 BAV           3
System reset line RESET 9*    
Common Ground line GND 10     GND      4
      Protect GND 6*
1.  Remember, you're looking at PINS!
2. Pin numbers marked with an asterisk are not connected when Dockbus and HEX-BUS are interfaced.
However if connecting a CC-40 to Dockbus peripherals, you'll need the power lines!
3. Caution! Pin #1 of DOCK-BUS is at +6 volts, supplied by the TI-74.  Pin #2 is used to supply all 
DOCK-BUS peripherals from a common power supply. This is not supported by the CC-40 system.
4. The Protective Ground (pin #6 of the CC-40 HEX-BUS should not be joined to 
the floating reference power line (pin #10 of the Dockbus).

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