Texas Instruments 99/4A Computer

[Startropic1]

I recently acquired an ancient Texas Instruments 99/4A computer that was basically collecting dust in my aunt's possession. (She's a college math professor.) It was humourous to see the oversized RF switch, which was actually damaged on the end that connects to the TV. The two clips, (yes it's that kind), were gone and there was nothing but a pair of wires exposed at the tips. I successfully stripped them further and wired them to one of those adapters you use to connect the old dual U connectors to a coax connector. So I now have the old dinosaur up and running. The box that the TI-99/A was packed away in had a bunch of old related computer books, several of which pertained to Basic. Also included were an "Extended Basic" cartridge already inserted in the front expansion cartridge slot, and an old data cassette deck ("Texas Instruments Program Recorder")--with one data casette. After taking a little time figuring out Texas Instruments' odd version of Basic, (very different from QBasic & the Basic used on our beloved Commodore computers), I attempted to load a program from the included data cassette; (it had "games" written on the label.) For whatever reason, the TI computer was unable to locate any program(s) on the cassette. I'm pretty sure I went through the loading process correctly.

So is anyone familiar with these TI computers? (Not to be confused with the well known line of calculators from the same company.) Also will the TI data cassette deck work with a vic-20? The cable used to connect it to the TI-99/A is a bit different than I remember having with the vic-20 data cassette deck, granted the last time I saw one of those was nearly 20 years ago.

[nbla000]

I recently acquired an ancient Texas Instruments 99/4A computer that was basically collecting dust in my aunt's possession. (She's a college math professor.)

I cannot help you btw I think this computer is quite rare.

[Schlowski]

At least more seldom than a VIC-20, according to the web it sold about 2 million times.

I don't think that the cassette deck will work unmodified with the VIC. Each home computer had it's own interface, so at least that would require some new wiring for the cable and for the right plug, I would expect.

But other than reading about the TI99/4A I have no experiences with that machine.

[Mikam73]

I have one

http://www.videogamehouse.net/gamemain.html

[RobertBe]

I have two TI-99 4/A's.

One with missing keys,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug
July 24-25 Commodore Vegas Expo 2010 - http://www.portcommodore.com/commvex

[Kweepa]

I have one here too.

I believe it uses the same video output scheme and plug as the VIC-20 so you can just plug your VIC-20 cable in, or use a 5-pin DIN to RCA cable and avoid the whole RF mess.

Can't help you with the cassette drive - I've just used cartridges.

[Mikam73]

Only at US. Here at Europe there is really mess getting composite/audio out of RF box. You need modify RF modulator to get composite out, it isnt possible directly from TI99/4A.

[nbla000]

wow it was the first domestic computer with a 16-bit processor on 1981 !!!

...and games were not too bad considering the age !

[Schlowski]

Yeah, it was a cool machine from the technical specs, but it was horrible from the implementation.

It had only 256 bytes of direct access RAM. Every other RAM had to be accessed byte by byte with writing low and high address to a register and afterwards reading or writing the desired byte to or from that address. (Similar to the VDC in the C128, I think - but for the whole RAM, not only for video RAM!) This was the so called GRAM which where only produced by TI so they could control the market and earn money from every single module.
As I read this resulted in the slowest Basic ever for any computer in that area, despite it's 16 bit processor! TI decided to. This is the reason why I decided to not give this machine a try even if it's specs sound promising at the start...

[Mikam73]

Speech was/is great

[nbla000]

It had only 256 bytes of direct access RAM. Every other RAM had to be accessed byte by byte with writing low and high address to a register...

what ?!?!

Thanks god to have suggested to my parents to give me a vic and not a Texas Instruments TI-99/4A

[Startropic1]

I have one here too.

I believe it uses the same video output scheme and plug as the VIC-20 so you can just plug your VIC-20 cable in, or use a 5-pin DIN to RCA cable and avoid the whole RF mess.

Can't help you with the cassette drive - I've just used cartridges.

I'm using a CRT TV, though it does have component inputs. (Also has standard RCA & coax)

The data cable for the data casette deck has 3 parts to it. It's Y shaped and in the middle, or solo end of the Y, is a typical female 9-pin serial connector like you would see on a vic-20 joystick (or atari or early sega controller.) At one of the split ends are 3 headphone type connectors, the middle of the 3 being slightly smaller, they are coloured white,black,red and numbered 3,2,1 respectively. On the other split end there are 2 similar headphone style connectors, with the same 2 different sizes. They're coloured red & black and numbered 4,5 respectively.

On the side of the tape deck itself there's a male 2-pin AC Input connector, a male 6V/DC connector, a white female connector labeled EAR-SPKR, a red female connector labled MIC, and a small female black connector labeled REM. There's also 2 dials on the same side, one labeled TONE and the other labeled VOLUME. When I connected the deck to the TI 99/4A I connected the 3-connector end to the deck itself, matching the coloured connecters. the serial connector plugs into the computer itself, and the end with the 4,5 connectors apparently just lays loose (perhaps for a possible 2nd tape deck or something.)

As I mentioned the deck seemed to work, but no programs could be read off the cassette I have.

[DanSolo]

I've got one here somewhere, and I'd be surprised if there's more than a handful within 100 miles. I have the RF converter thing but I don't have a power adapter for it .

[dano]

I have a few of them, several extra if anyone wants one. The "first" 16 bit home computer is the TI99/4 in 1979, the 99/4A is the improved version (and much much more common). You do only have 256 bytes of direct access ram unless you add a memory expansion card, which most people did. The rest of the memory is video memory, the video chip has it's own RAM. The cassette deck is just a standard one with a TI logo on it, like Tandy and others used. The system is pretty neat for it's day, but I kinda lost interest due to limited keyboard and the weird internals. Basically they took a CPU with a 16 bit bus and multiplexed it to 8 bits for all expansion, which of course slowed it down quite a bit. A popular hack was to add the expansion memory internally on the 16 bit bus and add some logic to remove the wait states for that memory range.

[zylon]

I have a few of these TI's. There's 2 DB-9 connectors on the computer. One on the back near power supply socket, and one on the far left side. Use the one on the rear of the unit and turn the volume up on the cassette deck.