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TI(ny)-99/4A Computer

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I don't know about Amazon, I don't use this company for my shopping. The case is based on the Corsair Carbide Air 240. I made some modifications to install the motherboard especially:
- The lowering of the metalic plan on which the motherboard is fixed, because of the TI-99 cards which are taller than the PC cards.
- Cutting the rear of the case for the 3 TI cards rear access.  
- Making a metalic cage for the two floppy disks drives.
- Cutting front plastic for floppy disks drives access.
- Making a cage for fixing the cartridge connector extender and the cartridge docking.

I must say that these modifications (done cleanly) are time consuming.

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  • 5 months later...
  • 2 months later...

Some months without news,  I'm sorry.

In May, two of my suppliers informed me that they couldn't provide me anymore the list of components that I planed to order. In addition,  the price of some IC grew significantly. I remember all the time I spent to find the least number possible of suppliers capable to provide all the components needed and offering NOS high-standard ones at he lower price as possible. I still haven't find the courage to redo the inquire...
Although the V2 motherboard development is ended. During these last months, I have considerably optimized the routing of the 4 layers PCB. Just for fun.
I can just say that the TIn-99/4A v2.6 is working well. I only use it since many months, without compatibility and stability problem.
I have found just one non-working game: Tutankham.

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Fabrice, on the chips, you might want to check Rochester Electronics. They are an authorized OEM for a lot of discontinued chips from other manufacturers, making certified replacements using the original chip dies once their supply of NOS chips is exhausted. Their prices are usually good on a per-chip basis, but their minimum quantities for a chip are sometimes very high (1,000+). I have an account with them and order a lot of chips that I haven't been able to find from other sources there (and it is good that they only supply certified original chips).

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  • 3 months later...

Thank you ?

 I have made low level tests that uses the specific V9958 graphic modes and the daughter-board well reacts: the VDP is well recognized.
To show you that the computer now accepts the new VDP, I used G99. But this program only uses GIF format. I don't know if there are programs (tools or demos) that exploit other things than the 80col mode and 256 colors features, like full color palettes in hi-res graphic resolutions. If some of you have other V9938/58 graphic programs, I'm interested!

I have hesitated a time before choosing the V9958 instead of the V9938. The first offers more colors, more hardware acceleration and higher resolutions than the second and that's great. But the second offers the mouse support... Hope I made the good choice.


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Fabrice is there chance to sell kit but you could choose what you want? I was thinking something like Harlequin 128 kit. It is on https://www.bytedelight.com/?product_cat=harlequin128.

You could put combination of kit or full system to sell. I know that you don't want to give all your hard work in form of gerber file and I think you have right to do so but maybe you can make range of products to choose with lower price.

Some form of kit or full system. You could put motherboard on sell in speed you want.

I respect all your hard work and I love your vision of TI99/4a.

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Thank you !

I think that the project is finally aiming to this kind of solution. There will be two configurations:

- A fully built motherboard & keyboard, ready to use.
- A motherboard populated with all components but the TMS9900, TMS9901, V9958, TMS5200 & PHROMS, MM58167, SN94624, MX key switches and caps, permitting to people that already have these components as spare to acquire the computer for a less price. The goal will also be for me to be sure that the motherboard sent has been fully tested OK.


 I have already tested a large quantity of programs and I near haven't noticed compatibility problem with the new VDP. At this time, the only non compatible programs found are Parallax from Retrospect and the Copper Demo from PeteE  (I am not surprised because it was especially made for the TMS9918A/29). Such a pity because I like so much this demo... Hope one day to see a V9938/V9958 version! ?


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19 hours ago, fabrice montupet said:

 I have already tested a large quantity of programs and I near haven't noticed compatibility problem with the new VDP. At this time, the only non compatible programs found are Parallax from Retrospect and the Copper Demo from PeteE  (I am not surprised because it was especially made for the TMS9918A/29). Such a pity because I like so much this demo... Hope one day to see a V9938/V9958 version! ?

I don't have access to a 9938/9958 to test, but the output signal is NTSC video, correct?  So the horizontal scan timings ought to be compatible.  Please send me a private message with a photo/video of the copper demo on the 9958 and the raster program from this post.  If anyone has a v9958-modded 99/4a in the Portland Oregon area, please contact me.

Edited by PeteE
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A lot of programs react on the same way with the V9958, I have noticed that with this new VDP some games are played a little bit faster,  it is pleasant. I have also noticed that some are more difficult like 'TI Rex' because obstacles are not moving at the same speed than with the TMS9918A/29. Hope that some games will not become unplayable on some levels. More annoying: I am encountering a problem with 'Sabre Wulf' from Rasmus. Here, the game is too fast, so fast that it is unplayable and the sprite collision is not detected. The introduction music is played very fast too.

Adding a V9958 on the computer is a great feature but I wonder if it will not prevent some people to play with some games (past and future) became unplayable... Maybe new games could propose to choose the VDP installed on the computer, but it will surely be a constraint for programmers because so few people have or will have the V9958.
Maybe a solution for the computer: I could put the VDP on a separate board, as an option, permitting to choose the VDP that one has chosen to use.  It will not be a card to plug 90° to a slot of the motherboard but  in the prolongation of it and without enlarge its dimensions (there will be a free space for it as we can see on a A500 motherboard for the expansion RAM) . It's just a thought.


Edited by fabrice montupet
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1 hour ago, PeteE said:

How did you fix the issue with sprite collision?

The sprite collision issue was just a silly mistake from when a made this version a few years ago. The root cause back then was that I tried to detect the F18A and thereby changed the current status register of the v9938, so it wasn't possible to read the VDP status byte. By setting the current status register back to 0 after the detection that issue was fixed. But I made a mistake trying to change the vsync detection from cru polling to vdp status polling, which I have reverted now. I'm not sure if poling cru bit 2 always works on v9938 enhanced machines, but at least it's working on TI(ny)-99/4A. Maybe other implementations of the v9938/c9958 are connecting the interrupt line directly to the CPU? @atrax27407 is it working for you now?

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  • 2 weeks later...

Finally, I have chosen the V9958 as the standard VDP of the computer. Hope that I have made the good choice.  And I have just finished its integration and the 128 Kb of VRAM on the motherboard. Of course, it will be possible to upgrade the VRAM to 192 Kb by piggybacking two DRAMs, I have placed a pin header for CASx). I had to greatly modify the routing of the motherboard, it was an opportunity to rethink the SAMS 1MB Memory Extension part (expandable to 4MB). Now a daughter card is no longer necessary, all the RAM memories of the SAMS extension are integrated into the motherboard (so an even more tiny motherboard ? ).

Note that the working V2.5 motherboard has a TMS-9918A/29A VDP

Here is a drawing showing the final organization of the TIny-99/4A v2.9. The presence of a cartridge gives a better idea of computer size:


Click on the picture to enlarge it.


These last modifications complete the development of the microcomputer...finally!



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