History of Plato educational system

The TI-99/4A is the first microcomputer with the Plato educational system first by a cartridge based interpreter with disk based lessons and later with a rs232 based Plato terminal program that connected to the main Plato system via modem.

This modem based terminal was never really available to the public so was basically forgotten about in the TI-99 community.

Then in recent years Thomas Cherryhomes set up a Plato environment and has made it a priority to revive the micro computer terminals for many systems. He got ahold of the original terminal software and posted on the  Atariage TI-99/4A forum looking for help testing the original terminal software. I downloaded a copy from him and was able to test it connecting to his irata.online Plato server with a wifi modem. There were some incompatibilities with the terminal and irata so Thomas decided to rewrite the terminal in C using the newly created GCC port for TMS9900 development.  He was able to get it together but when testing found that the TI-99/4A rs232 port was unable to handle the data rate requirements so he decided to make the terminal use the telnet protocol over the TIPI device designed and built by Matthew Splett. You can download and use this terminal with an expanded 99-4A with 32k RAM expansion and TIPI


You can connect to https://irata.online ‘s Plato system from your TI-99/4a with TIPI installed with this command: CALL TIPI(“PI.HTTP://TI99.IRATA.ONLINE/PLATO”)

You can connect to https://www.cyber1.org/ ‘s Plato system from your TI-99/4A with TIPI installed with this command: CALL TIPI(“PI.HTTP://ftp.whtech.com/TIPI/PLATOC”)

Note: For those without TIPI hardware, the Classic99 Emulator supports the TIPI networking stack and will work with this, just run the commands above in basic and you will be using Plato in no time.


HEX-TI-r HEXBUS disk drive emulator assembled and tested

This is a HEXBUS emulation running on an Arduino Uno board with add-on clock/sdcard board.


Power on HEXTIr

Connect HEXBUS cable (key points up on devices made by arcadeshopper.com)

Power on CC-40

You should see an activity light on the HEXTIr board blink when the CC-40 handshakes.


  • catalog command: OLD “100.$”
  • list will provide a listing of the catalog

Loading programs:

  • OLD “100.FILENAME.EXT”  – loads FILENAME.EXT  from the device

Software repo: https://github.com/go4retro/HEXTIr

TI-99/4A FAQ: Archiver

Archiver 3.03, often abbreviated as Arc303, is the TI’s equivalent of ZIP files they are compressed files that usually contain more than one other files inside them.
Usually these end with an ‘@’ character to indicate they are archived, although some PC distributions may use a .ARC or .ARK extension instead. To extract the files, you will need a copy of Archiver 3.03 found at http://ftp.whtech.com

TI-99/4A FAQ: Text Adventure Games

Adventure cartridge – Scott Adams adventures

https://www.mocagh.org/loadpage.php?getcompany=ai&npp=25&whatsnew=0&start=0&series=TI-99%2F4A+Adventures+Series  has a nice list of the games available for this cartridge. You need a cassette player/cable or disk system to load the games with the adventure module. No other expansion is required it works fine on stock console.

Adventure Games:

Others listed: https://intfiction.org/t/list-of-games-in-scott-adams-ti-99-4a-format/49771

Return to Pirate’s Isle

This game is unique as it was only created for the TI-99/4A (officially adventure #14) and it is the first graphical adventure game published for home computers.


Infocom officially released the following games for the TI-99/4A

  • Zork I
  • Zork II
  • Zork III
  • Enchanter
  • Sorceror
  • Deadline
  • Witness
  • Starcross
  • Suspended
  • Planetfall
  • Hitchiker’s Guide to the Galaxy
  • Infidel
  • Cutthroats
  • Sampler

The TI community has released an updated interpreter that supports all of the original games plus additional

  • Ballyhoo
  • Suspect
  • Leather Goddesses of Phobos*
  • Spellbreaker
  • Seastalker

A recent infocom compatible release was made that includes a TI-99/4A release

Hybernated – 1 https://atariage.com/forums/topic/321529-for-fans-of-old-infocom-games-something-new/

TI-99/4A FAQ: Abbreviations

By Dan H. Eicher
    AVPC - Advanced Video Display Processor, produced by Digit Systems
            (Tom Spilane) - This PBOX card use an 9938. 
    c - Small C by Clint Pulley for the 99/4a.
    E/A - Editor Assembler.
    FDC  - Floppy Disk Controller. 
    FWEB - Funnel Web.
    GRAMULATOR - Graphics Ram Module produced by Cadd Electronics
                 allows the user to load/modify and run cartridges.
                 Unlike the GramKracker produced by Millers Graphics
                 with modifications, this unit could also run MBX
    GRAM KRACKER - See Gramulator.

    Grand Ram - A ramdisk produced by DataBiotics. Unique in that 
           it both battery backed up like a Horizon Ramdisk and 
           provided print spooler software (like the Myarc 512K)
           card. It also included connectors on board to connect
           to emulate the PBOX bus and cartridge port.
    GROM - Graphic ROM  
           Rom Memory developed by TI that automatically increments.
    HFDC - Myarc Hard Floppy Disk Controller.
    MBP - Eight port analog to digital card with real time clock.
    MBX - Milton Bradley Expansion Unit (yes the toy maker) allowed 
          the 99/4a to use voice directed games.
    PBOX - Peripheral Expansion Box also known as PEB.

    PC99 - A software package for MSDOS PC's (486-50 or faster) that
           emulate a TI99/4A. This is commercial software and well 
    PGRAM - Like the GramKracker, but on a PBOX card. 
    PIO - Parrallel/Printer Port.
    POP-CART - Cartridge produced by OPA that up to 512K of grom
               code and any number of cartridges could be placed.

    SOB - Son Of a Board. This board also plugs into the console,
          in the GROM1 socket. It adds an enhanced menu upon power
          up and fixes some video initialization problems that are
          transparent, unless you are using a 9938 or 9958 video 
          controller chip in your system. 
    TIM - TI Image Maker. This is a an 80-column board produced by 
          OPA. It had a Yamaha 9958 chip and came bundled with the
          SOB. It mounts inside the TI console in the TMS9918 socket.

    V9t9 - A software package for MSDOS PC's (386-25 or faster) that
           emulates a TI99/4A. This is freeware (produced by Ed. 
           Swartz) and no support from the author is available,
           but the source code is.
    XB  - Extended Basic.

TI-99/4A FAQ: Sidecar expansions

Many Sidecar Expansions were made for the TI-99/4A:

TI Sidecars:

  • Speech Synthesizer
  • 32k Memory Expansion
  • SS/SD Disk controller
  • RS232
  • PCode
  • Video Controller
  • Solid State Thermal Printer

Corcomp Sidecars:

  • CC9900 Micro Expansion System
    • The 9900 Micro expansion from Corcomp provided 32k and also an optional board can be installed to provide a DSDD disk controller and RS232/PIO ports
    • Power Supply  5 pin DIN
  • Corcomp Clock
  • Corcomp 256/512k Ramdisk

Myarc Sidecars


Other Sidecars

  • Boxcar Peripherals RS232
  • Axiom ParallAx Printer Interface
  • Triton Turbo XT

Homebrew Sidecars

  • JediMatt42
    • 32k RAM Sidecar
      • https://jedimatt42.com/ti32kmem.html
    • TIPI Sidecar (ram card with 44pin required)
      • https://github.com/jedimatt42/tipi/
  • Arcadeshopper
    • SAMS 1mb Sidecar
  • Jgparker
    • 32k/TIPI combo card
      • fits in original speech synth case (after removing original board) also 3d printed cases are available
      • https://github.com/jgparker/tipi

TI-99/4A FAQ: Power Supplies

External Power Supplies:

  • TI-99/4A USA: 

Internal Power Supplies:

Power supply from a 99/4 (NOTE: NOT COMPATIBLE WITH 4/A)

Power supply from a 99/4A

Power supply from a 99/4A QI


This is the connector on the back of the console that the ac adapter plugs into. Some of these connectors have 4 pins, while others have 3. The newer power supplies (QI) only have 2 pins. They way they were set up you can use any ac adapter with any of the consoles.

The AC voltages in are:

1. Black 8 volt

2. White 16 volt

3. Red 5 volt

4. No connection

The power supply is a very standard setup, and could be replaced by any standard PC power supply.

The DC voltages out are:

Pin 1 = -5 volt

Pin 2 = +12 volt

Pin 3 = GND

Pin 4 = +5 volt.

No AC Voltage? check the fuse!

TI was required by the UL to add a fuse to the external power supply. Their solution? add a pigtail to the power cord with the fuse in a little plastic box.

These fuses tend to blow after so many years of use, so the fuse needs to be replaced or just remove the pigtail if you are using a power strip with built in circuit breaker making the fuse unnecessary.  You will find it’s just stuck on the old plug with some adhesive and it should come apart with some effort.

Fuse type:  4/10A 250V 


Schematic for power supply (not QI)

Here is an interesting project replacing the console power supplies with a new board:


TI-99/4A FAQ: Extended Basic

Extended Basic Module from Texas Instruments

  • The Extended Basic module was not included with the console and was semi-expensive originally. 
  • Extended Basic exists in two distinct versions, Version 100 and Version 110. To determine which you have us this small program:
      • 10 CALL VERSION(A) :: PRINT A
    • Only a very small handful of the earlier Vn 100 were sold. 
    • Principal difference is speed: Version 110 is much faster.
    • Version 110 fixes bugs and supports sprites and features on the 4A that were not available on the 99/4
    • EXTENDED BASIC is a much larger language than TI Basic.
    • The increase in operation speed is not shown by magazine ‘bench tests’ which use very short specific programs. In a typical program you will find the program runs in about 30% less time. Line transfers and screen handling are particularly faster than in TI Basic. This is due to the fact that some of these routines are in assembly language in Extended Basic while TI BASIC is 100% GPL. 
    • Extended Basic also adds any new commands and functions over TI BASIC enabling better use to be made of limited memory, and also permitting friendlier programs to be written.  
    • Extended Basic allows for multiple commands per program line using  :: as a command delimiter
    • Extended Basic supports the 32k memory expansion allowing 24k to be used for program data, the rest of the memory is used for stack.
    • Many TI BASIC programs can be loaded in Extended Basic, and will then run faster.
      • Exceptions are:
        • TI Basic programs over 12k cannot be loaded due to lack of memory. (memory expansion doesn’t help with this due to TI BASIC programs load into VDP ram only)
        • Some TI Basic programs will load but cannot RUN due to lack of memory.
        • TI Basic has two extra character sets: if these are used, they will produce a BAD VALUE error in Extended Basic. Extended Basic uses the memory saved by dropping these sets (15 and 16) to produce the Sprites
        • Extended Basic manual: https://www.digitpress.com/library/manuals/ti994a/ti%20extended%20basic.pdf

Versions and variations on Extended Basic:




TI-99/4A FAQ: Terminal Programs

The most feature rich terminal program for the 4/a is TELCO.. This supports ANSI graphics (NO COLOR) and 40 and 80 column modes (80 column requires a 9938 or greater VDP and does not work currently with F18a 80 column mode) Multiple file transfer protocols, printer spooling etc..

This file contains a disk image, pdf format manual and keyboard overlay http://ftp.whtech.com/communications/Telco%20-%20Complete%20Package.zip

Other terminal programs and their features

Term80 – 80 column terminal on stock VDP, uses a TINY FONT but supports color ANSI and high baudrates using specialized rs232 routines and memory devices for buffering data..  buggy and incomplete but still pretty cool

MXT – Mass Transfer – allows for multiple file transfers and standard ascii terminal emulation , xmodem included as well this has also been ported to work as a telnet client for TIPI

Fast Term – ASCII terminal program that works up to about 19200 baud..

Terminal Emulator and Terminal Emulator II – cartridge based terminals support 110 and 300 baud, 7 bits even parity and has a proprietary terminal emulation mode allowing for graphics and sound,  also only supports file transfers from TE compatible systems (TIBBS FOR INSTANCE)