March 2006

TI99 Computer

TI-99/4A Home Computer

I purchased my first home computer in the Fall of 1979. After using an Apple II computer at work and investigating what was available, I decided to buy a Texas Instruments TI-99/4 computer. This was the first 16-bit personal computer, based on TI’s 9900 processor used in business computers. It also had several technical capabilities not seen in other personal computers. It had an accuracy of 13 digits based on its Radix 100 notation and a method on context switching found in Control Data mainframes. Unfortunately, it also used a double-interpreted BASIC making it slow since the base machine was programmed in GPL, a Graphic Programming Language.

My first TI-99/4 computer cost about $2500 with all the accessories. TI included a video monitor with the original console. It had a total of 16K bytes of memory built in, used programmed cartridges and stored BASIC programs on a cassette tape. I then added a 32KB memory expansion, an RS232 interface, a disk controller with two 5 1/4” floppy drives. These were all “sidecar” boxes about 7” wide, which along with a Speech Synthesizer and the 15” wide console, resulted in a computer train about 39” wide. [See the picture on the Home page.]

Later, TI came out with an upgraded TI-99/4A model and a Peripheral Expansion Box (PEB) that contained cards for each expansion connected to the console through a wide, shielded ribbon cable. The picture included here actually contains the 4A model with two PEBs that also contain two 5 1/4” floppy drives, a 3 1/2” floppy drive, a p-Code PASCAL card and an IDE interface card connected to a 2 GB hard drive. The bottom PEB is actually used just for its power supply and to mount the 3 1/2” floppy and hard drive. The IDE interface and HD were just added in December 2004. The console also has a cartridge expander that allows switching between three cartridges.


thursday, 02 march 2006 18:00


Last night, I started checking my computer inventory for a modem that my sister could use to access the internet. I told her I would set her up with an old PC that I had, but discovered it had no modem built-in. I knew that I had a 56KB modem around here some where, but I have not found it yet. But what I did find was amazing, taking me back to 1979 and showing the changes that have evolved in home computer communications since then.

By the way, the term modem is short for modulator - demodulator. This is a way to convert a computer's digital data in a manner to transmit it over telephone lines. In the early days, this was done with an acoustic coupler in which a telephone handset was placed. These were built into old Teletype machines like I first used in 1969. The one shown here is from my first TI 99/4 home computer that I bought in 1979. These typically worked at 150 or 300 baud (bits per second). I also found other hardwired modems running at 1200, 2400, 4800, 9600 and 14,400 baud. As the technology advanced in speed, these would negotiate the highest speed they could operate on with the modem on the other end of the telephone line. When you dialed to connect to another computer, you would hear this chirpy, hashy noice, increasing in frequency until it matched what the other modem and the quality of your telephone connection could handle.

Starting around 2000, I have had Qwest DSL service that ran at about 256 Kbaud. Though I upgraded to their Deluxe DSL which was supposed to run up to 1.5 Mbaud, it never ran at half that speed and degraded back down to about the 256 Kbaud level last year. Finally, in December, I switched over to the Time-Warner Road Runner cable internet service. This evening, the cable modem speed has varied between 1.5 Mbaud and 4.8 Mbaud, probably averaging around 3 Mbaud. Imagine, over the last 25 years, we have experienced a 10,000 times increase in speed at least with a typical home computer. Dedicated commercial lines and the main internet trunk networks operate at much higher speeds.