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fabrice montupet

Texas Instruments Dimension 4

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Who own this early version of the 99/4 computer?

I would be happy to see its innards, and especially under the top cover hole (optional Infrared feature) :-)

Hope it has the TMS9900 CPU modification instead of TMS9985 too!

 

X720-86.1.lg.jpg

 

Another picture of it, picked-up in a video:

ti994bta.jpg

Edited by fabrice montupet

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When the Dimension-4 was being conceptualized and tinkered with, TI were trying to use the 8-BIT chip, but it was unreliable. I have read somewhere there were two or more Dimension-4's with Zilog Z80 chips in them, but staff were shuffled around and they never went further with Z80.

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Fabrice, I am reasonably sure that the prototype 99/4 parts that I have came from a Dimension 4, based on the date of manufacture (late Dec 1978 to late January 1979, based on the chips it contains, the integrated Video modulator, and the connections that were supposed to go to the IR receiver in the top of the case). Mine has a TMS9900 in it though it could easily switch between processors based on the modular design of the motherboard. The main board has very few components on it, but all of the interconnects to the various ports are there. The processor and the VDP and all of their controllong circuitry are on a smaller daughter board that plugs into the main board. I really need to make a set of detailed pictures of this beastie, as it may be the only one of them outside a museum (and this one DID come from a museum that threw its old TI computer collection away, with the bits I have rescued from a recycler who dismantled the machines and threw away all of the parts he saw no use for a few months/years before I found out he had them).

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One note--the Solid State Software badge goes deep into the history of the 99/4--as it is also on the Dimension 4. . .one has to wonder why they planned for the possibility of two different sound systems at that early date. . .

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@Retrospect: Yes, the earlier version of the 4, before they integrate the TMS-9900 have many technical issues, the TMS-9985 originally planned was buggy and not fully operational.
I had never heard / read about a Zilog Z80 CPU in a TI-99. Are you really sure about that? Because, the Texas Instruments politic was to use its own processors and micro controllers.

 

@Jim: Your description corresponds to what I know about the early TI-99/4. Your motherboard is equiped with a TMS-9900 daughter board, it dates of the period when TI realized that the TMS-9985 will never ready to a mass product. Your pictures to come will be a pleasure for my eyes and I don't know how I will be able to sleep before you post them :-)

Thank you so much to have saved this computer.

 

Maybe someone has kept the TMS-9985 daughter-board. I hope so!

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I thought the Z80 rumor was that the engineers created a mockup, rather than it actually being considered for production?

 

And yeah! I'd love to see the daughterboard and even more love to see a 9985 ;)

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I could be wrong but it's hard to believe in a project (even an idea) based to a Z80 in a TI-99/4.
Use "foreign" CPU was not in the DNA engineers, nor that of the management team of Texas Instruments. But they (forced to) change their mind due to the steamroller IBM PC

Edited by fabrice montupet

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I could be wrong but it's hard to believe in a project (even an idea) based to a Z80 in a TI-99/4.

Use "foreign" CPU was not in the DNA engineers, nor that of the management team of Texas Instruments. But they (forced to) change their mind due to the steamroller IBM PC

I know, I found it hard to believe TI would consider it, but I read it somewhere within a series of letters penned to another TI guy, these are available on the net somewhere but I can't remember the path I took to find it. Maybe ftp site documentations deep within I think. I'm sure TI did have a policy of using it's own chips, so that's what made it hard to believe.

 

EDIT:

 

They may have been attempting the Z-80 for future CP/M compatability, as they knew at the time the Z80 was used quite widely for business, it can clock over 6MHz in some cases.

Edited by Retrospect

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Or they were just evaluating alternatives to the failed 9985 CPU. Engineers love to experiment more than stick strictly to policy, and TI didn't /have/ an 8-bit processor. Dropping a Z80 in there as a prototype would have taken a day at best (though there'd be no software). Could have just as easily been a thought experiment. ;)

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@Tursi: I think that if one of the engineers has launched the idea to put a Z80 in the 99/4 to the team , there was a witchcraft trial for the guy ;-)

 

@Restrospect: Yes, the Z80 was popular, as the 6502, the 6800 or the 8080 at the end of 70's but TI wanted to create its own standard of computer and not be a follower or an actor behind the curtain.
TI didn't care CP/M neither during the developpement of the TI-99/A nor for its future: no CP/M PEB card has been planned by TI. The goal was to propose a personal computer not a professional one. Even the -never released- TI-99/7 computer destined to the professionals was not CP/M compatible. Texas Instruments always prefered to propose UCSD Pascal.

Edited by fabrice montupet

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@Tursi: I think that if one of the engineers has launched the idea to put a Z80 in the 99/4 to the team , there was a witchcraft trial for the guy ;-)

 

@Restrospect: Yes, the Z80 was popular, as the 6502, the 6800 or the 8080 at the end of 70's but TI wanted to create its own standard of computer and not be a follower or an actor behind the curtain.

TI didn't care CP/M neither during the developpement of the TI-99/A nor for its future: no CP/M PEB card has been planned by TI. The goal was to propose a personal computer not a professional one. Even the -never released- TI-99/7 computer destined to the professionals was not CP/M compatible. Texas Instruments always prefered to propose UCSD Pascal.

 

That's pretty much how I remember reading it, as well. Referring to The Orphan Chronicles, the first home computer (which never existed beyond a few circuit-boards in the lab of TI Consumer Products Division) did actually use a foreign processor. When this was presented to management, as you correctly say, there was a feeling that buying CPUs from either Zilog or CMOS was aiding the competition, and they didn't want to get into a situation where a competitor could play tricks such as delivering inventory late (on purpose) etc. So, they looked internally to see what was around that they could use. Originally, the 9985 was chosen [it is my belief that the 9985 would have run GPL at the CPU level, rather than an interpreter in ROM] but it proved to be a failure. That really only left them with the 9900, but the 9900 was far to expensive to buy in from the Computing division (can't remember its official title). Then they looked at the actual cost of the TMS9900 to TI as an organisation. They realised that if they could buy the CPU "at cost to themselves" (partial quote from The Orphan Chronicles from my (faded) memory) then the numbers worked, and they could get a much more capable processor under the hood for the same price as an externally sourced 8 bitter.

 

The reality was somewhat different. The entire board was based around an 8 bit bus, and the software guys had totally run away with themselves and based the system software on a virtual machine language (GPL) that didn't exist in real Silicon. So the 9900 fitted in like a pork sausage at a jewish wedding.

 

Then they gave it Microsoft and said "Hey, put a BASIC on this, will you?"

 

Thus proving the concept that you can put lipstick on a pig, but it's still a pig :grin:

 

Oh well. C'est La Vie :-)

Edited by Willsy
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This is very metaphorical, but the facts are given ;-)
The TI-99/4, (and its successor 4A) is a failed computer, its structure is tortured, 8bit in some parts, 16bit in other... It's terribly complicated, absolutely not optimized. But the TI engineers succeeded the stroke of genius to adapt the TMS-9900 into a motherboard absolutely not designed for it. The result is impressive. I love this computer :-)

 

Oh! you speak french! It's so sweet :-)

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On ‎8‎/‎10‎/‎2015 at 3:57 PM, Willsy said:

Then they gave it Microsoft and said "Hey, put a BASIC on this, will you?"

Everybody interviewed claims that this part never happened. The BASIC in the TI 99/4A is instead based on the BASIC available for the TI-990 mini computers.

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4 hours ago, apersson850 said:

Everybody interviewed claims that this part never happened. The BASIC in the TI 99/4A is instead based on the BASIC available for the TI-990 mini computers.

We are only allowed to restart that debate once every 4.7 years. ;)

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19 hours ago, Tursi said:

We are only allowed to restart that debate once every 4.7 years. ;)

I'm not done finding evidence for my hypothesis that TI-99/4A Basic is based on the Basic for the 990.

 

I've written a few programs on Dave Pitts' 990 simulator, but what I really want is to disassemble the interpreter.

 

It just amazes me that recently, I'm finding fascinating things about this 40 year old phenomenon.

 

 

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On ‎8‎/‎10‎/‎2015 at 2:05 PM, fabrice montupet said:

@Tursi: I think that if one of the engineers has launched the idea to put a Z80 in the 99/4 to the team , there was a witchcraft trial for the guy ;-)

 

@Restrospect: Yes, the Z80 was popular, as the 6502, the 6800 or the 8080 at the end of 70's but TI wanted to create its own standard of computer and not be a follower or an actor behind the curtain.
TI didn't care CP/M neither during the developpement of the TI-99/A nor for its future: no CP/M PEB card has been planned by TI. The goal was to propose a personal computer not a professional one. Even the -never released- TI-99/7 computer destined to the professionals was not CP/M compatible. Texas Instruments always prefered to propose UCSD Pascal.

 

It is not really inside the TI-99/4 or /4A console, but in the PEB (and think it runs on its own like the UCSD Pascal),

but last week I came along a person in the TI community who has these cards: Foundation Z80 card for the PEB.

 

Not sure if someone has the CP/M card

 

I only have these scans I found when digging through a huge pile of copies.

 

Z80-Foundation-02.thumb.jpg.b7f8ce0533182d74eb4717ce0a83127f.jpgZ80-Foundation-01.thumb.jpg.a95a31ce9bf026bdf6e590376ba0a1a0.jpg

 

CPM-05.thumb.jpg.aae3218cc764448c5dc712add8b6a816.jpgCPM-03.thumb.jpg.466f23b8bab1ee85a085a21e602f7bc8.jpg

CPM-04.thumb.jpg.717f0b0376c1c6dd22f5b3e5c99f69d0.jpg

 

CPM-02.thumb.jpg.7f14fbe192510134b5d40c171af22039.jpgCPM-01.thumb.jpg.eaad7012fd7e28a9f42f308ec1d05462.jpgZ80-Foundation-03.thumb.jpg.67bc04a6462b7324f8011321d5ee0d99.jpg

 

 

 

 

 

 

 

 

Edited by globeron
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4 hours ago, globeron said:

It is not really inside the TI-99/4 or /4A console, but in the PEB (and think it runs on its own like the UCSD Pascal),

It's more like the Geneve. The UCSD p-code card is just a memory card, with 60 KBytes of ROM/GROM. It's still executed by the TMS 9900 in the console.

This card has its own CPU (Z80), just like the Geneve has its own TMS 9995.

 

Interesting to see their timing comparisons with the TMS 9900 and the Z80. The TI fails miserably, but a lot of that is due to the memory architecture in the 99/4A, not the CPU itself.

The TMS 9900 would do the first example in 7.3 us, when memory is at full speed, and has more "registers" available.

In the second example, they use the fact that the Z80 has a block move instruction. Still, with no wait states limiting the TMS 9900, and taking advantage of that it's a 16 bit CPU, thus moving a word at a time, the 9900 will still complete that sequence in 7 ms. So in this case the long time is both due to slow memory and inefficent programming.

Edited by apersson850
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5 hours ago, globeron said:

 

It is not really inside the TI-99/4 or /4A console, but in the PEB (and think it runs on its own like the UCSD Pascal),

but last week I came along a person in the TI community who has these cards: Foundation Z80 card for the PEB.

 

 

 

 

 

If they can make an image of any software packages, OS or whatever, that would be fantastic.

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7 hours ago, apersson850 said:

It's more like the Geneve.

There is still a difference. The Geneve is to some extent compatible with the TI-99/4A. It can run almost all of its programs.

 

Browsing over the pages, I wonder how the CP/M card gets access to the VDP in the console.

 

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We definitely need an image (or at least copies) of the Foundation CP/M disks. I have a card but not the OS, so I have never been able to test it. . .I've never seen anyone with one of the Morning Star cards, unfortunately. Apparently, only a few were actually sold--and the majority of the run remained in a basement somewhere in Colorado, hostage to an angry spouse. . .who wanted to see reasonable return for the major funds expended to produce them in the first place (full price or no sale).

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I had an acquaintance in the '80s, I had done some work for... At my request, they ordered a TI-99/4a replacement for me(from Triton) ...through a friend... whom they referred to only as MORNINGSTAR! Same on box. Probably unrelated though... Hmmnn!:ponder:

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I will be selling my Dimension 4 at the end of this month unless I sell it at DFW Retro computer gathering on jan 25 in Dallas. Power light still comes on but haven't got any video to output in recent efforts but it did output previously. 

 

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I am definitely interested in purchasing this. . .and I suspect Fabrice is just as interested.  :)

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