Introduction: What is a TI99/4?

But what many people (including many TI99/4A fans) do not know is that before the famous 4A, TI released another home computer, the TI99/4.

Similar in many ways to the more popular 4A (but with some surprising differences!), the 99/4 was the first computer that I ever used, and having come into my life roughly 18 years ago, it was undoubtedly a part of what eventually led me to become a computer programmer by profession.

There are now many pages out there dedicated to the 99/4A (see my links section below), but as of this writing I've yet to find a web page dedicated exclusively to the 99/4. Therefore, here is my tribute to the "the one I started with, but sadly could not stay with..." (with apologies to TI's early 80's ad campaign).

(The image above was scanned from my copy of the original TI99/4 User Reference Guide.)

What were the differences?

• The Keyboard.

  The most obvious difference between 99/4 and 99/4A was the keyboard. While the 4A had full-sized proper "typewriter"-like keys, the 99/4's keyboard only had plastic (not rubber as falsely noted in some documents) keys, shaped like "chicklets" (the keys keys with flavour flavour?). In that way, it was similar to early Tandy Coco keyboards, or the first IBM PCJr keyboard. The 99/4's keyboard had a total of 41 keys: 1-0, A-Z, ".", one red ENTER, one red SHIFT, the space bar and an extra SPACE key to the left of the "A" key!

  More important though is that the functionality of the keyboard was very different from the 4A. The TI could type in uppercase only. And it had no FUNC key. Instead, functions were activated by using (gasp!) SHIFT! For example, to break out of a program, you hit "SHIFT-C". I can not overstress how dangerous this was!!! I remember at least one occasion where "SHIFT-Q" was hit by accident at the start of the word... "SHIFT-Q" was effectively the equivalent of an ALT-CTRL-DEL today! Hours of typing down the drain! (Okay, okay, I should have been saving my work, right? I was a kid, I know better now...).

• Keyboard Overlays

  As a side-effect of the difference in keyboards, the TI 99/4 used entirely different keyboard templates from the 99/4A. The 99/4's templates (referred to as "Overlays" in the manuals) were brown sheets of thin plastic that fit over the entire keyboard.

  

• Differences in the ASCII Character Set
  Since, as noted above, you could only type in uppercase, the TI 99/4's ASCII set did not have any lowercase letters defined. When the 99/4A came out, it had the added ability to let the user type in lower case, so the ASCII set was expanded to cover the extra characters. The expanded ASCII on the 4A also added the {,}, and ~ characters.

• The Equation Calculator

  In addition to the ROM-resident TI BASIC, the 99/4 had another built-in program called the "Equation Calculator", that was not found in the 99/4A. The Equation Calculator was a nifty calculation tool that allowed the user to process algebraic expressions, similar in functionality to the popular TI programmable calculators available at the time. The program always came up as option 2 on the 99/4's master selection list, meaning that the cartridges came up as option 3. The Equation Calculator could explain why the 99/4's ROM was 5 kbytes larger than the 99/4A's.

• The Graphics Chip

  An important difference between the 99/4 and 99/4A was the graphics chip. While the 99/4 and 99/4A apparantly used the same CPU (the TMS9900 3.3MHz), they had different display chips. The 99/4 used the TMS9918 and the 99/4A used the TMS9918A. This gave the 99/4A an additional display mode, although that display mode was not accessible from TI BASIC. However, this is most likely the main reason that I could never get PARSEC to work on my 99/4...

• Earphone Jack

  The TI99/4's case included a built-in 1/8" mono earphone jack at the front left edge of the unit. I'm not sure what the use of this was, but you could plug in an earphone or walkman-type headphones into this jack and hear the sounds from the TI directly instead of from the TV's speaker. Obviously, TI thought this was of dubious value as well, as it was nowhere to be found on the 99/4A. I've recently been informed that not all 99/4s had this jack, and there was apparantly in fact a variation that included a speaker in the casing, in front of the cartridge port!

• Power Supply

  The TI99/4 apparantly did not use the same power supply as the 99/4A. Unfortunately, I've yet to find out exactly what the difference was between the two - can anybody supply this information? All I know is that a 99/4A power supply does not work on a 99/4, and in fact one of the 99/4As that I own has a warning in the documentation telling the owner not to use a 99/4 power supply on their 4A!

• Cartridge port

  Jim Fetzner e-mailed me this one: The port for the cartridges places the connector about 1/4 inch closer to the opening on the 99/4 than on the 4A -- Nothing major right?? Not until you try to take a cartridge built specifically for the 99/4 and insert it into a 99/4A -- whereupon, it will not make contact! James has only seen one cartridge where this really makes a difference, one called Preschool Early Learning Fun -- note that this is NOT Early Learning Fun (He has both cartridges, and they are very different).

• Copyright Date

  A minor difference: The 99/4's start-up screen noted the copyright date as being "1979", whereas the 99/4A's screen had "1981".

TI 99/4		TI 99/4A

TI 99/4 - related links

If you are looking for 4A information, try The TI 99/4A Home Computer Page or the TI 99/4A Shrine. Both of these pages are excellent and contain many other links to TI99-related pages.

There is a Usenet NewsGroup dedicated to TI home computers! Point your newsreader to comp.sys.ti.

Fans of other "obsolete" computers should check out The Obsolete Computer Museum or The Machine Room.

My TI 99 collection

I more recently obtained two TI99/4A systems, one an original silver & black model, and one the later white model. Unfortunately, I only have one RF modulator and it doesn't work very well. Finding a new RF modulator is at the top of my wish list for TI items right now!

For a complete list of my current TI hardware and software, as well as my VIC 20, C-64 and Intellivision items, click here.

Written: Jan 08, 1998 This is version 2.00 updated: Jan 07,1999 Comments to author: Andrew Gurudata guru@vex.net Mississauga, Ontario, Canada Click on Gazoo to return to my home page.

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