Category Archives: TI-99/4A

Hardware/software for the TI-99/4A

Internal power / disable switch for the Axiom Parallax printer interface

The Axiom Parallax sidecar Centronics printer interface has only nine chips inside, and they’re all small LS TTL glue. The console +5VDC supply should be able to handle the additional (minimal) current draw, especially if the console has an F18A … Continue reading

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Printing from a TI to a modern printer

So, obviously, the TI-99/4A doesn’t support printing to USB printers, nor can it print to network printers. With a little help, though, it can print to modern printers via a helper device running UNIX/FreeBSD/etc. This leverages the BeagleBone Black-based cassette … Continue reading

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Two UberGROM images: Logo/Logo-II/Multiplan/TurboForth and Plato/Return to Pirate’s Isle

Thanks to Tursi, Ksarul, and a few others, it’s now possible to create bankswitched GROM/ROM cartridges for the TI-99/4A. Most of the game cartridges were converted long ago to disk-loadable EA/5 images (most needing the 32k RAM expansion). The languages, … Continue reading

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Building a TI-99/4A cassette deck emulator

Although many people use their PC (workstation-class) to transfer programs to their TI via playing a .wav into the cassette port, I went in a different direction. I like small dedicated devices, and thus I built a tape recorder emulator … Continue reading

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HRD+ 74259 Daughterboard verified good

The subject says it all, really. I got ahold of a couple of 74LS259D SMD chips, soldered them into the adapter board, and replaced the ‘259 stack in the HRD+ with the daughterboard. Since nothing ever works correctly the first … Continue reading

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Daughterboard replacement for Horizon HRD+ chip stacks

Earlier, in my article about refurbishing an old Bud Mills Horizon HRD+, I asked why TI gear (both official and homebrew) tended to stack similar chips on top of each other, straightening pins out, and using flying wire to connect … Continue reading

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Why I am against RAM-based DSRs

Right, so there’s a non-negligible number of TI users that use hardware with their DSRs (device-specific firmware) in battery-backed RAM. This is a horrible, HORRIBLE idea … but I’m apparently having difficulty communicating to various users exactly why it’s a … Continue reading

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Refurbishing a Horizon HRD+ RAMdisk Card

I recently came into possession of an ancient Horizon HRD+ RAMdisk card for the TI-99/4A PEB. Not the 2000, 3000, or 4000 — the original model, designed by Bud Mills and Ron Gries circa 1986. It’s a variable-size RAM disk … Continue reading

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Why won’t the TI-99/4A cassette port work with my PC sound-out port? Here’s why …

TL;DR: the OEM TI cassette cable tape-audio-1-input jack is wired incorrectly for equipment available now. Leave pin 9 floating and run pin 3 to CS1 plug sleeve and things magically work. You can cheat by amplifying the signal a lot … Continue reading

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The TI-99/4A PEB flex-card “tune-up”.

The fellow at mainbytes.com has had an article up for the past decade that recommends that few TTL chips in the flex-card that connects the TI-99/4A console to the PEB should be replaced with CMOS equivalents, and swap a few … Continue reading

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