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Index
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Model:
TI-99/4A
Release Date:
June 1981
Original Price:
$525
Processor:
TI TMS 9900 3.3 MHz<
Memory:
16 KB RAM / 26 KB ROM
This is one of the first computers that I ever had the opportunity to really delve
into. I remember sitting in class at school with a binder open in front of me as I
poured over the BASIC and Extended BASIC manuals - all the while the teacher is
rambling on about something or other. I spent a lot of time writing programs for that
computer. Unfortunately, I can no longer find that binder.
In addition to the console itself, there was also a speech synthesizer unit available
that would plug into the right hand side. Although I still have that unit, I must
have gotten it pretty late in my TI days. I don't remember ever hearing it speak, even
though I did have the game "Alpiner" that I understand would have made it
work. I'm going to try and get it going, though. The voices created by this unit
are said to be of pretty realistic quality. If you happen to have one of these,
you'll notice there is a door that opens on top. It was intended for cartridges to
increase the synthesizer's vocabulary, but was never used due to the success of
text-to-speech software in "Terminal Emulator II". If your unit happens to
have the connector under the door, you have a rarity indeed!
Other peripheral offered included a 5¼" floppy disk drive and controller, an
RS-232 card with two serial ports and a parallel port, a thermal printer, an
acoustic coupler, a cassette tape drive, and a 32kb memory expansion card. The
problem with the peripherals is that they were connected to the console through a
daisy-chain type connection - where each unit plugged into the next. That would be
fine as long as you only had one or two options, but start stringing three or four
or more together and you'd find yourself running out of desk space! To help
combat this problem, TI released the "Peripheral Expansion System" (also
known as the "Peripheral Expansion Box" or "PEB"). This was the
fore runner to the modern ISA and PCI expansion card model. This case was made of
a two-ply thick-gauge steel chassis housed in a cast aluminum case. It included
it's own unregulated linear power supply, a full-height 5¼" floppy bay and
eight card slots.
Additionally, there were dual digital joysticks that were connected to the console
through a single 9-pin game port. This was to ensure only TI authorized controllers
would be compatible. Aftermarket adapters were later released that allowed two Atari
style joysticks to be used. I was lucky enough to find a pair of the original TI
joysticks brand new at a yard sale this past weekend. They were still in the
styrofoam packaging but the box was missing. For 75 cents, I can't be too picky.
2.8 million systems were sold before the TI-99/4A was discontinued in March of 1984.
>>
Click here to download the User Reference Guide (7.29 mb)
>>
Click here to download Beginner's BASIC (5.23 mb)
>>
Click here to download Extended BASIC (9.5 mb)
>>
Click here to download the Technical Data Book (7.05 mb)
>>
Click here to download a collection of sales literature (11.2 mb)
>>
Click here to download the schematic diagram (935 kb)
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Pinouts:
Power Connector
Pins 1 & 2 = 16 vac 2amp
Pins 2 & 4 = 8 vac 0.16amp
Pin 3 not connected
Audio/Video
Pin 1 --- N/C
Pin 2 --- Ground
Pin 3 --> Audio Out
Pin 4 --> Composite Video (NTSC)
Pin 5 --- N/C
Cassette Interface
Pin 1 --> Cassette 1 Motor Control (remote)
Pin 2 --> Cassette 1 Motor Control (remote ground)
Pin 3 --> Output to Tape 2 (microphone)
Pin 4 --> Audio Gate (?)
Pin 5 --> Output to Tape 2 (microphone ground)
Pin 6 --> Cassette 2 Motor Control (remote)
Pin 7 --> Cassette 2 Motor Control (remote ground)
Pin 8 <-- Input From Tape 1 or 2 (earphone)
Pin 9 <-- Input From Tape 1 or 2 (earphone ground)
Joystick Port
Pin 1 --- N/C
Pin 2 --> Test Joystick 2
Pin 3 <-- Up
Pin 4 <-- Fire
Pin 5 <-- Left
Pin 6 --- N/C
Pin 7 --> Test Joystick 1
Pin 8 <-- Down
Pin 9 <-- Right
| Card Slot |
Front Rear |
| Pin 01 --- +8vdc | Pin 31 --> Address12 |
| Pin 02 --- +8vdc | Pin 32 --> Address13 |
| Pin 03 --- GND | Pin 33 --> Address10 |
| Pin 04 --- ReadyA | Pin 34 --> Address11 |
| Pin 05 --- GND | Pin 35 --> Address8 |
| Pin 06 --> RESET | Pin 36 --> Address9 |
| Pin 07 --- GND | Pin 37 --> Address6 |
| Pin 08 n/c SCLK | Pin 38 --> Address7 |
| Pin 09 n/c LCP | Pin 39 --> Address4 |
| Pin 10 <-- Audio Input | Pin 40 --> Address5 |
| Pin 11 <-- RDBENA | Pin 41 --> Address2 |
| Pin 12 -H- PCBEN | Pin 42 --> Address3 |
| Pin 13 -H- HOLD | Pin 43 --> Address0 |
| Pin 14 n/c IAQHA | Pin 44 --> Address1 |
| Pin 15 -H- SENILA | Pin 45 -H- AMB |
| Pin 16 -H- SENILB | Pin 45 -H- AMA |
| Pin 17 <-- INTA | Pin 47 --- GND |
| Pin 18 n/c LOAD | Pin 48 -H- AMC |
| Pin 19 <-> Data7 | Pin 49 --- GND |
| Pin 20 --- GND | Pin 50 --> CLKOUT |
| Pin 21 <-> Data5 | Pin 51 --> CRUCLK |
| Pin 22 <-> Data6 | Pin 52 --> DBIN |
| Pin 23 <-> Data3 | Pin 53 --- GND |
| Pin 24 <-> Data4 | Pin 54 --> Write Enable |
| Pin 25 <-> Data1 | Pin 55 <-- CRUIN |
| Pin 26 <-> Data2 | Pin 56 --> Memory Enable |
| Pin 27 --- GND | Pin 57 --- -12vdc |
| Pin 28 <-> Data0 | Pin 58 --- -12vdc |
| Pin 29 --> Address14 | Pin 59 --- +12vdc |
| Pin 30 --> Address15 | Pin 60 --- +12vdc |
| |
| -H- above means that the line is always high |
| Cartridge Port |
 |
| Pin 01 <-- RESET | Pin 19 --- +5vdc VCC |
| Pin 02 --- GND | Pin 20 --> Address8 |
| Pin 03 <-> Data7 | Pin 21 --> GS |
| Pin 04 --> CRUCLK | Pin 22 --> Address7 |
| Pin 05 <-> Data6 | Pin 23 --> Address14 |
| Pin 06 <-- CRUIN | Pin 24 --> Address3 |
| Pin 07 <-> Data5 | Pin 25 --> DBIN |
| Pin 08 --> Address15 | Pin 26 --> Address6 |
| Pin 09 <-> Data4 | Pin 27 --> GRC |
| Pin 10 --> Address13 | Pin 28 --> Address5 |
| Pin 11 <-> Data3 | Pin 29 --- -5vdc VDD |
| Pin 12 --> Address12 | Pin 30 --> Address4 |
| Pin 13 <-> Data2 | Pin 31 <-- GR |
| Pin 14 --> Address11 | Pin 32 --> Write Enable |
| Pin 15 <-> Data1 | Pin 33 --- VSS |
| Pin 16 --> Address10 | Pin 34 --> ROMG |
| Pin 17 <-> Data0 | Pin 35 --- GND |
| Pin 18 --> Address9 | Pin 36 --- GND |
| Side Port |
 |
| Pin 01 --> +5vdc VCC | Pin 23 --- GND |
| Pin 02 --> SBE | Pin 24 --> PHI3 |
| Pin 03 --> RESET | Pin 25 --- GND |
| Pin 04 <-- EXTINT | Pin 26 --> Write Enable |
| Pin 05 --> Address5 | Pin 27 --- GND |
| Pin 06 --> Address10 | Pin 28 --> MBE |
| Pin 07 --> Address4 | Pin 29 --> Address6 |
| Pin 08 --> Address11 | Pin 30 --> Address1 |
| Pin 09 --> DBIN | Pin 31 --> Address0 |
| Pin 10 --> Address3 | Pin 32 --> Memory Enable |
| Pin 11 --> Address12 | Pin 33 <-- CRUIN |
| Pin 12 <-- RESET | Pin 34 <-> Data7 |
| Pin 13 <-- LOAD | Pin 35 <-> Data4 |
| Pin 14 --> Address8 | Pin 36 <-> Data6 |
| Pin 15 --> Address13 | Pin 37 <-> Data0 |
| Pin 16 --> Address14 | Pin 38 <-> Data5 |
| Pin 17 --> Address7 | Pin 39 <-> Data2 |
| Pin 18 --> Address9 | Pin 40 <-> Data1 |
| Pin 19 --> Address15 | Pin 41 <-- IAQ |
| Pin 20 --> Address2 | Pin 42 <-> Data3 |
| Pin 21 --- GND | Pin 43 --> -5vdc VDD |
| Pin 22 --> CRUCLK | Pin 44 <-- Audio In |
All Pin-Outs Are Courtesy of
the Hardware Book Project
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