The cheapest PC of all time: The Timex Sinclair 1000

Wed 21 Mar 07 20:34 | Tags: Hardware, Retro

Behold the Timex Sinclair 1000.

I can't entirely recall how and when I came into acquisition of this little guy; I suppose I "collected" it during a point in my life when I had more money than sense, and unlike the TRS-80 Model 100 I wrote about earlier, I doubt I had a practical use for it when I got it. But I still have this one, and after coming across it in my closet earlier today, I decided to go ahead and hook it up for the first time and see what it can do.

The unit next to a marker for size reference. (It's small.)

The specs

First, a little background info on this machine. It's actually a rebranded US version of a computer released by the British company Sinclair Research Ltd, which made several computers during the early '80s which were popular in the United Kingdom and few places else. Sinclair's original version of the machine, released in 1981, was called the Sinclair ZX81, and was the follow-up to a machine released in 1980 aptly called the Sinclair ZX80. It featured a 3.25MHz Zilog Z80 processor (though it performs much slower in reality; more on that later) and a single kilobyte of RAM. Yes, one single kilobyte; 1024 bytes of memory. For comparison, the text of this article takes up over 12KB. I'm well aware that the resource needs of the standard computer user have risen over time, but still, I can't imagine how a personal computer with 1KB of RAM could be at all useful to anyone; with that little memory, how could you write a letter to your mother (including the overhead for a word processing app) and print it out? An optional first-party add-on module increased the RAM to a much more usable 16KB, though, since much of the commercial software released for the ZX81 required the RAM module to run, perhaps "optional" is the wrong word. The module was quite large and connected to an external connector on the back of the unit. Timex's version, released stateside a year later, doubled the ram to 2KB, but you still needed the module to do anything serious.

As you can see in the picture above, the unit is quite small. One of the reasons for that is that many of the features which were common for personal computers at the time were not present on this machine; there's no sound hardware and no dedicated video hardware. The port for the memory module served as the device's sole expansion or serial port; expansion devices had a pass-through connection on the end of their cable which allowed the device and the memory module to be used at the same time. This bare-bones design helped push the cost of the machine down to US$100 when it was released, making it the most affordable new personal computer of all time (though I suppose that could depend on how exactly you define the term "personal computer").

This machine did not support a floppy drive, but instead had "speaker" and "mic" ports which you connected with audio cables to the corresponding ports on a cassette recorder to store and retrieve data from an audiocassette. It also has a "game-style" video output. And… that's it.

Living in Sinclair

Okay, enough with the stats; let's open the box. What I had in there was different than what originally came in the box when the system was new. The 16KB memory module was included; it looks like the previous owner knew what they were doing. There was also a cassette with financial programs on it, and a power adapter. The video switch and cassette recorder cables were not included.

Ah, memories of the days when you had to do a contortion act behind your TV set before you could play Ms Pac-Man.

The first thing I needed to do to hook this baby up was to find a game switch. Remember these guys from the old Atari 2600 days? Of course you do. Fortunately, I still had a newer version of one of these which has a 75-ohm coaxial output as well as the 300-ohm forked antenna connector output; the earlier versions of these only had the latter, and I no longer own or have access to a TV I'd be able to connect that to. Okay, so I connected the power adapter and video switch to the wall, then plugged in the adapter and connected the video. I did not connect the memory module, since I wanted to see what it would be like to compute with such little RAM. I looked over the device for a moment to try to find where the power switch was; it turns out there isn't one. Unplugging the device is the only way to turn it off. Yet another example of skimpy design…

So I set the TV to the proper channel, and was presented with a blank white screen with a prompt at the bottom. Cool, it works. I was also greeted by an annoying buzzing sound; as I said, the ZX81 has no sound hardware, but instead of just outputting no sound, it outputs a buzz. Apparently some clever coders found a way to modulate the buzzing noise in such a way to output very basic music from the machine, but it couldn't have been pretty to hear. Mute!

I began to enter some BASIC commands into the machine. As you can see, the device has a membrane keyboard that, in a word, stinks; I pity anyone who had to do serious typing with this thing. I found it easier to type by holding the unit between my hands and using my thumbs to press the keys, thumbboard-style. Unsurprisingly, "real" keyboards and keyboard adapters were among the most popular third-party accessories for the system. One of the biggest frustrations is that "Delete" is not its own key; the top row of the keyboard stops at 0 (zero), and to delete, you have to press Shift-0. Many frustrating times I would try to delete and find I was entering a series of zeroes instead. Also, the keyboard is surprisingly missing any way to enter an exclamation mark or apostrophe; these characters were apparently not present in the ZX81's character set. The charset also did not feature lower-case letters, though it did feature inverted video letters. More reasons I can't imagine anyone being able to write a decent letter to Mom on this thing.

HI MOM. HOW ARE YOU? GUESS WHAT? MARIA AND I ARE EXPECTING A BABY. YOU ARE GOING TO BE A GRANDMA. IS NOT THAT EXCITING?

Fortunately, entering in BASIC commands with this keyboard is eased a bit by the keywording functions of the system; it's smart enough to expect when you'd want to enter a BASIC function name or other keyword, so you can just press one button to enter it. These are the words shown in white text on the keyboard. So you could type "GOTO" just by pressing the G key; very handy.

My Sinclair 1000 did not come with a manual, but fortunately I found a scanned version of it online. (Yes, it's probably copyright infringement, but somehow I can't see Timex caring much nowadays; they've gone back to making watches.) I used it as a reference to write up the BASIC program below. The intent was to create a string which became longer and longer until it maxed out the machine's meager RAM. The system's BASIC interpreter is surprisingly capable for such an otherwise pathetic machine.

10 LET X=0
20 LET X$=""
30 LET X$=X$+STR$ X
40 CLS
50 PRINT X$
60 LET X=X+1
70 IF X=10 THEN LET X=0
80 GOTO 30

If you ever dipped your toe into BASIC, you can probably figure out what this does. If not, here's the gist; it stores "0" into memory, prints it out, and clears the screen, then stores "01" to memory, prints it out, and clears the screen, stores "012", prints, clears, stores "0123", prints, clears, ad infinitum. Okay, so let's run it. (QuickTime, 3.5MB -- sorry for the low quality here; I had to use my digital camera and do a screen cap, since I don't have any hardware which can capture video from coax.)

The 16K memory module (note the size) and a data cassette.

Hmm. It's pretty slow, isn't it? Well, remember above where I said that the machine had a Z80 processor? That's actually a decently powerful little chip; Nintendo used a 4.2MHz Z80 in the original Game Boy, and Texas Instruments still uses them today in most of their graphing calculators. So why can't it perform as well here? Well, remember when I also said that the system has no dedicated video hardware? That means that the Z80 also has to handle the system's monochrome video output. It manages this by synching itself with the television's CRT scanning mechanism; when it's moving from its starting position to its ending position, the processor tells the TV what it needs the picture to look like. Only in the brief moment when the TV is not actively drawing pixels as it moves its electron gun from the end position to the start again does the processor actually execute the program. This continual "distraction" of the processor causes it to run dog slow. Sinclair mitigates this somewhat by including a "fast mode" feature which basically stops the processor from processing video and allows it to focus entirely on the program, at the cost of causing the picture to flicker as the TV is no longer receiving instructions on what to draw from the system. When the program issues a pause command, needs input from the user or terminates, the machine goes back into "slow mode" to show the user what's happening. Since my program isn't using fast mode, it's going to execute dog slow. With this system, you can have fast processing or you can have smooth video, but you can't have both at the same time. ("Fast" and "smooth" of course being very relative terms here.)

I left my little program running while I took the pictures you see in this article. When I came back to it, it was still chugging along. (6.6MB) I finally gave up and issued the Break command to the program. I guess 2K of RAM is actually plenty when it takes the program this long to fill it up!

Back in the box

The box.

Finally, I decided I had enough fun. I disconnected the system, packed it back into its foam tray, slid the tray back into the tattered box and chucked the box back into my closet. I don't exactly know what I'm supposed to do with this thing; they're going for a pittance in eBay auctions, even for more-complete sets, so I'd rather not deal with that. I suppose I'll just wait until the next free electronics recycling day in my town, then pitch it in.

The ZX81 managed to be a big hit for Sinclair, and likewise the Sinclair 1000 put Timex on the personal computing map -- undoubtedly aided more by the low price tag than any technological capability of the machine. Sinclair repeated their success in 1982 with the release of the ZX Spectrum, which offered more memory, an improved keybaord, and very elementary color graphics support. Timex released the Spectrum in the US as Sinclair 2068, but it failed to catch on in the American market, and by 1984, Timex was no longer releasing personal computers in the US. Personally, I don't think the personal computer market in the US is that much poorer for the fact.

References

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#1 | Shane | 24 Apr 07 13:21

Yup, we had one. Dad brought it home. We had either 2-16k or one 32k pack on it. We had few programs for it, the 2 I used the most were Flight Simulator, and some Word Processor.

In 4th Grade I handed in a 3 page paper from it, the printer for it was thermal paper so I had to glue it 2 column style to 8x11 then photo copy it.

Wow, memories.

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