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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 1st Feb 2019, 7:59 pm   #1
electronicskip
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Default Texas Ti99/4a out of hibernation.

On a snowy day I decided to take my Texas Ti99/4a computer out of hibernation.

It's not actually been turned on for a number of years so I was a little apprehensive, but took the plunge and hoped for the best.

Powered up fine with no problems, so I popped in a couple of carts Ti extended basic and also Ti invaders which powered up with no problems with good pictures and sound.

Spent a good few hours with this great computer I'd forgotten how decent the graphics and how good the actual keyboard was as well.

Does anyone else out there have an affinity with this system?

Apologies for the poor photos.
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Old 2nd Feb 2019, 11:03 am   #2
SiriusHardware
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Default Re: Texas Ti99/4a out of hibernation.

I missed out on these when they were contemporary as they were never quite as widespread as the Spectrum, C64, BBC B.

Many moons ago I bought a ZX81 in an immaculate Dktronics keyboard / enclosure from a fellow forum member and was then offered a Ti-99 as well, which I declined on the grounds that my taking it would deprive someone who really wanted it. I sometimes regret that decision but I know it would have been like so many of my other old machines: Maintained in perfect working order, but rarely if ever used.
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Old 2nd Feb 2019, 11:41 am   #3
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Default Re: Texas Ti99/4a out of hibernation.

That's my problem, I'm exactly the same, I've got a loft full of these old machines dating from about 1972 but rarely used or even looked at.

My next power up is going to be my immaculate Philips G7000 Videopac unit .
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Old 2nd Feb 2019, 1:56 pm   #4
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Default Re: Texas Ti99/4a out of hibernation.

I had a friend who had a TI-99/4A, and my experience of it was disappointing compared to the British computers of the day. The BASIC language was rather limiting, there seemed to be no way to use machine code, it did not have pixel-addressable graphics (certainly not accessible via BASIC, although maybe some of the cartridge games might have managed this -- my memory is unclear) and the character set was ugly (though could be redefined). It was almost as though the whole point of it was to get you to buy software cartridges, and the ability to program it yourself was just thrown in as an afterthought.

By contrast, the Spectrum (not the prettiest charset either, but we all came to love it anyway), BBC and Amstrad machines all had pixel-addressable graphics and came with comprehensive manuals that encouraged you to write your own programs, and it was easy to use machine code (especially on the BBC Micro, with its built-in assembler).

The Commodore 64 and Atari 800 also had less comprehensive BASIC languages than the British machines; on the C64, you had to POKE addresses directly to access the sound and graphics. The British machines had a BEEP or SOUND command that accepted parameters for pitch (directly in semitones above or below middle C) and duration, and PLOT and DRAW commands for creating graphics. (The Spectrum and Amstrad also had a CIRCLE command; the only shapes the BBC could draw were triangles -- and any other shape that could be made out of triangles!)
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Old 2nd Feb 2019, 7:23 pm   #5
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Default Re: Texas Ti99/4a out of hibernation.

I seem to remember that the TI99/4A had very little RAM on the processor bus (256 bytes or something). There was 16K of RAM on the video chip (a TMS9918 in the States, possibly a TMS9927 over here) and BASIC programs were stored in that and then interpretted by the processor, being read a byte at a time via the video chip

This mean no user machine code on the standard machine (there was nowhere to store it, you couldn't run machine code programs via the video chip) and it was rather slow.

I think one of the expansion cartridges added conventional RAM which made the machine a lot more useable.

Incidentally the same video chip was used in the Tatung Einstein computer but that machine had 64K RAM on the processor bus (as well as the 16K on the video side) so it was a lot more useable. The video RAM on that machine also stored the definitions of user-defined keys I think.
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Old 2nd Feb 2019, 9:02 pm   #6
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Default Re: Texas Ti99/4a out of hibernation.

Yeah, I later read that there was something weird about the memory architecture on the TI machine. That's probably why programs ran slower than an incontinent three-legged dog in a lamp post showground. No wonder, if it's got to fit a line of BASIC plus the BASIC an processor stacks (the BASIC stack has details of FOR loops and RETURN addresses for GOSUBs on it, plus whatever is being involved in calculations being done) into 256 bytes. Presumably software on cartridge is mapped directly into the CPU's address space, so the full VDP RAM becomes available for bit mapped graphics?

In the UK, we probably were spoiled; our home computers were ready to go out-of-the-box, without having to fork out for extra hardware just to make it usable. Or maybe it's that we were too tight to buy upgrades, so manufacturers had to make the machines more than just good enough to begin with!
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Old 2nd Feb 2019, 9:56 pm   #7
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Default Re: Texas Ti99/4a out of hibernation.

Quote:
Originally Posted by julie_m View Post
In the UK, we probably were spoiled; our home computers were ready to go out-of-the-box, without having to fork out for extra hardware just to make it usable.
Not too sure about that, 1K RAM on the standard out-of-the-box ZX81? Someone did manage to write a chess game which ran on the 1K machine but that was rightly considered to be miraculous. For any serious purpose you needed more.

Our American cousins, on the other hand, got 2K RAM as standard on their version of the machine.
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Old 2nd Feb 2019, 10:40 pm   #8
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Default Re: Texas Ti99/4a out of hibernation.

Most of us ended up buying the 16k ram pack for the zx81.
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Old 3rd Feb 2019, 12:34 pm   #9
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Default Re: Texas Ti99/4a out of hibernation.

My two ZX81s, one of them the above mentioned Dktronics-housed one, the other my original machine in its original housing, are both expanded to 16K onboard memory using 62256 SRAMS.

One half of the 32K chip is 'wasted' due to the simplicity of the mod, but there is no practical reason to need more than 16K on a ZX81, as no commercially made software ever expected to find more than that.

It has the great advantage of making the machine rock stable - no more ram pack wobble - and restores the undeniable good looks of the basic machine while making it genuinely usable.

I'm very surprised to learn about the primitive memory arrangements on the Ti-99. I suppose putting the RAM in the cartridges kept the base machine (relatively) cheap and raised the price of the cartridges, which obviously the company hoped you would buy a few of once you had committed yourself by buying the machine.

Didn't they ever produce a simple 'extra RAM' cartridge?
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Old 3rd Feb 2019, 1:09 pm   #10
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Default Re: Texas Ti99/4a out of hibernation.

There are two RAM Carts listed, one an 8k and another of 32k.
I've never actually seen them in the wild however and when I used to sell the Texas computer we never stocked them either.
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Old 4th Feb 2019, 12:14 am   #11
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Default Re: Texas Ti99/4a out of hibernation.

It looks like there is at least one recent third party implementation of extra RAM for the Ti-99:

http://ti994a.cwfk.net/32k.html
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Old 4th Feb 2019, 8:09 am   #12
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Default Re: Texas Ti99/4a out of hibernation.

Quote:
Originally Posted by SiriusHardware View Post
It looks like there is at least one recent third party implementation of extra RAM for the Ti-99:

http://ti994a.cwfk.net/32k.html
One is mentioned here too

http://oldcomputers.net/ti994a.html
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