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TI(ny)-99/4A Computer

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This project is firstly a fun that I wanted to develop since many years and that was regularly postponed because of many other projects I wanted to realize too.
This TI(ny)-99/4A is the computer that I dreamed to have in 1983. Of course, it only integrates components that were available in 1983 :-)
I wanted this project a personal work, no any kind of help outside the original TI TI-99/4A schematics. The goal was that this project be as didactic as possible. For many years, TI schematics have been precious to repair my TI-99/4A computers. My detailed study of them will show me that they were not reliable: Several errors slipped inside. The first step was a precise study of the logic of the microcomputer in order to detect all the errors. It was a very interesting step.
Once the TI-99/4A schematics were corrected, I begun the design of the TI(ny)-99/4A motherboard and the integration of all the improvements defined initially.


TI(ny)-99/4A technical datas:
TMS-9900 @ 3 MHz or 3.58 MHz
RAM: 32 Kb
Internal GROM: TI-Basic and Editor/Assembler
VDP TMS-9929A + 16 Kb VRAM (double VDP extension planned, a protoboard tested OK)
RGB video output (with pots for adjustments)
Slot connector for PeBOX cards
Speech Synthesizer CD2501/TMS-5220
Extended keyboard - 63 keys (pictures will come soon)
Joysticks ports (Atari type)
TI Joystick connector (onboard)
Low-profil case ( 34 cm x 26 cm x 7 cm)


You can see my TI(ny)-99/4A Computer here: http://www.ti99.com/ti/index.php?article136/ti-ny-99-4a


Note: The first picture is showing the computer equipped with a floppy disk controller in order to run the "Don't Mess With Texas" demo (the E/A is onboard)

Edited by fabrice montupet
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That is a really nice piece of work, awesome job! The PCB looks completely professional, to the point that I wonder if you do PCB layout for a living? Very very nice implementation. I'm wondering what you used for the case? Also, are you planning to release the corrected schematics? I'm not sure anyone was aware that the TI schematics for 99/4A had errors... At lease I did not.

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Thank you so much for the compliments you made about my TI(ny)-99/4A Compuler.

I began to trace the TI schematics to a PCB design software. But as and when I progressed, I encountered strange values, tensions or lines on the original TI schematics. So, at one point, I put aside the TI documents to work exclusively on my own board and improvements. I haven't listed all the modifications that I applied. Contrary to my other projects, I have not made a wire wrap prototype board, I directely design the PCB with a software. So, it permits me to easily bring modifications, improvements and to reproduce the board as I want. For this v.1.0 motherboard, I lauched the production of 5 PCB.
In the near future, I will propose populated motherboards (with no case). To help eveyone to fit the motherboard into a case, I design it with ATX specifications for holes and size.

Yes, I made the case from scratch, it was funny to do.

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I don't know of any other way to put it other than that motherboard looks beautiful, particularly how neatly arranged it all is. And the finished assembled product looks great too, kind of like a VCR or Beta player. Amazing what is being done these days with vintage computing by hobbyists. Great job!

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This is pretty close to what I want but a newer VDP would break your 1983 rule.

I would also go with newer RAM just for long term availability and to save board space, but again... 1983.


I understand his passion for period hardware and specifications. I love his concept and building skills. Like you if I had the skills or money to get it done, I'd probably have 1 meg SAMS capability built-in as well as wireless keyboard interface and a licensed version of an expanded F18A with HDMI output. Possibly even TIPI compatibility as well. I mean really, if I'm going to fantasize I might as well think big right? While we're at it, might as well throw in a microSD card based SSHD type of arrangement and do it all of this in surface mount for a smaller footprint.

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I'm definitely in for a PCB if they become available! I've been wanting to experiment with connecting TI hardware into a coin operated arcade cabinet to use as a platform for making new 80's style coin-op games, the RGB out on this board to simplify things greatly.

Edited by Tornadoboy
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