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Timex Sinclair ZX81 Back On the Market 266

Eugene Blanchard writes: "You still have the chance to purchase that Timex Sinclair ZX81 computer. Someone has kept a warehouse full of them. I had a few and thought that they would make a pretty good controller board with the Z80 processor. Now let's see if we can load Linux on them! "
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Timex Sinclair ZX81 Back On the Market

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  • Sinclair had probably the most absurd advertising campaign running in the UK. One advert ran that claimed that the ZX81 could run a nuclear powerstation. Hmm wonder if the Russian ever run a modified ZX81 for their nuclear stations... rampack wobble could have a lot to answer for. Sadder still there were companies advertising strip poker games for the ZX80 & 81, could you image that in block graphics Is it true the rumour that the Spectrum/Timex 1000 used failed chips from McDonnel Douglas Fighter Aircraft ?. ps. Anyone remember playing 3D Monster Maze ? Arguably it was one of the first 3D games, hardly wolfenstein or doom but surely it had to be a defing moment in gaming history.
  • Sinclair really made it with ZX Spectrum which was one of these "famous" micros (among c-64 and Apple)

    ...and I've still got two of those knocking around somewhere. I've been toying with the idea of trying to implement some form of networking on it (such as 9600bps SLIP), but I don't think I'd ever seriously get round to it. Especially since I'd have to write it in Z80 assembly...

  • My mum queued up in WH Smiths (UK newsagent chain) on the day the ZX81 came out to buy one; ready assembled. I must admit that before I saw this article on Slashdot I was confident that only the earlier white ZX80 was supplied in kit form; but seeing the other posts here, especially those mentioning a ten pounds price difference between assembled and kit, does stir some kind of vague memory.

    I sold my ZX81 to buy a hard drive for my Atari ST (having gone through a C=64 on the way). Luckily I was recently given a replacement ZX81 complete with 16k wobblepack which now sits proudly on the black and white TV in my computer room (I'm colour blind so quite handily I already had an ancient UHF B&W telly).

    My important question is: can you save ZX81 programs to .AU or .WAV files? Or even MP3s?


  • The Spectrum, running a later version of Sinclair's BASIC, also had a VAL$ expression, which evaluated a string as a string expression. I only ever saw it used once, to print various parts of a string array based upon a varying index, for a BASIC Frogger clone. A loop calculated the enormous string expression, storing it in a string. The main loop incremented the index, then used VAL$ to evaluate the string.

    I also used the memory saving techniques on my Spectrum, when memory was tight. Usually this was when the location of the stack was lowered to allow machine-code instructions to be placed where the stack couldn't smash it. One method of saving memory in basic was to assign a constant used more that 3 times to any unused single-character variable. Made the code utterly unreadable, but saved a few precious bytes.

  • You must not forget that Taco is one that selected this for posting. The other same submissions that does not include's prolinux statements are filtered out to suit Slashdot's bias.

  • HOLLY: I was in love once -- a Sinclair ZX-81. People said, "No, Holly, she's not for you." She was cheap, she was stupid and she wouldn't load -- well, not for me, anyway.
    LISTER: What are you trying to say, Hol?
    HOLLY: What I'm saying, Dave, is that it's better to have loved and to have lost than to listen to an album by Olivia Newton-John.
    CAT: Why's that?
    HOLLY: Anything's better than listening to an album by Olivia Newton-John.

    -Red Dwarf, Season 2, Episode 1: "Stasis Leak"
  • Can you imagine.... ...a beowulf cluster of ZX81s? (sorry, but it had to be said!)
  • I'm sitting in front of my PC here that has 96meg of RAM. If I bought that much in the form of 16k RAM packs like the ZX81 here uses it'd cost me over 130,000 pounds.

    I guess 80 pounds for 128meg is a decent price after all.
  • I had one. Parsec, Munch Man, Blasto... I even had the Scott Adams Pirate Adventure. How could you not say those games rocked? Oh, and I had the speech synth too... the pinnacle of coolness at the time. It even did digital audio, one game I played (a Frogger clone) used the speech synth to make the frog do a realistic "ribbit, ribbit".
  • I still have the original - complete with it's modifications. It still works!

    It was what got me started with computers so I have kept it. A friend also gave me their old ZX81 which is in mint condition.

    I also have a Spectrum but I daren't use it often because of their PSU circuits have a design snafu which can fail catastrophically.
    I still also have the motherboard to my old IBM PC/XT with a massive 64K on board.

    Sigh - nostalgia!

  • Hmmm, never had the fortune to have all that add on stuff, but Parsec was fun. But then I got my old system working again a couple of years ago, and found that my skill had somewhat improved; just kept playing it until I was so totally bored.

    The TI99/4 was, I understand, the first 16 bit home computer available to the mass market (predating the IBM PC by about 2 years). The 4A was a fairly simple upgrade.

  • Zebra Systems is for real, they've sold this stuff for 20 years now. Call them up tomorrow...
  • The Z80A in the ZX81 (UK version) ran at 3.25MHz. The Z80A in the ZX Spectrum ran at 3.5MHz.
  • Silly me. Posted this response to the wrong thread.
  • Actually, there are two POKEs... one doubles the access rate to ROM and the other doubles the access rate to RAM. Doubling the RAM rate disabled the video controller's access which also meant disabling the DRAM refresh cycle -- if the cpu stopped accessing memory for more than 4 microseconds, interesting things would happen.

    The COCO3 was designed differently and always ran at the full 1.7Mhz clock rate.

    Trivia factoid: the 68B09E uses a quadrature clock so it's speed is comprable to that of a 4MHz 8086.

    I had an email from Kevin Darling (Date: Wed, 12 Dec 90 07:11:03 GMT) claiming to have heard of a 15MHz version. I cannot find the electronic version; I've only got a printout of it. (After 10 years, the archive is hard to search.)
  • Alas, what ever happened to Zenith?
    Alas, I threw mine out last month before moving to a new job. That thing was pretty cool though, had StarOffice and everything for it. But I hadn't even turned it on in 5 years and I seriously doubted I ever would again... too bad, I might have sent it to you.
  • Woah, the 102 is kind of like... an ANTI palm pilot.

    It sure would be fun to carry one of these around as a joke.

  • and I think that was the Sinclair's situation as well.

    I remember having to add RS-232 buffers to the C64's otherwise perfectly good serial port, and (with the exception of Radio Shack) many of the others failed to provide a usable serial port.

    My production Timex model got warm, but not too badly.
  • Probably much too late for this to get noticed now, but...

    Is there an archive of ZX81 software anywhere, possibly in WAV or MP3 format?

    The best by far is zx8 1/ [], part of World of Spectrum []. These are generally RAM images, rather than tape images.

    Other places worth going are the comp.sys.sinclair [comp.sys.sinclair] newsgroup, and its FAQ [] (although this is more ZX Spectrum biased. And maintained by me :-)).


  • I've got a couple of Betamax VCRs and a video-disc player if you're prepared to pay 3k for the lot.

    I'll even throw in an LED digital watch and calculator - plus a couple of hundred batteries to get you through the first week.

  • There are some zx81 emulation sites with game images, so there must be a way to do it : maybe play the audio tape into a sound card ? The encoding is only FSK, like a 300 baud modem.
  • by goat_attack ( 127983 ) <goatattack@no t s o h o t> on Thursday October 05, 2000 @06:40PM (#727529)
    Imagine a beowulf cluster of these things! ;)
  • Has anyone tried this???

    The cassette recorder leads you get with the ZX-81 (and spectrum) will plug straight into a PC sound card. You can then load and save the stuff as audio files. (And distribute them on Napster (if MP3 compression does not screw things up)).

    Also, any ZX-81 hackors out there???

    I'd love to see "3D Monster Maze" modified to include a rocket launcher...

    "Rex is approaching..."

    "Rex has seen you..."

    "Run he is right beside you..."


  • by Steve Smithies ( 23419 ) on Thursday October 05, 2000 @06:43PM (#727531)
    Heres a link to a page with details for building your own ZX80/ZX81 from scratch: tml []
  • The Game Boy uses a processor similiar to the z80, but it is not a true z80. It is missing all indexing instructions (IX/IY), 16 bit loads, port instructions (IN/OUT), shadow registers, and some other that I'm forgetting. The GB processor also executes instructions differently than the regular z80, making the timings completely different.

    Check out this site for more info: []
  • I don't believe it, I got my Uncle to sell a couple of ZX81's for me on a trip to India in the late 80's as there was still a market for them then. I think he got about 50 quid ($75ish) for the two of them!!
  • Rumor had it (or so I heard) on the Trash-80 that there was also an instruction that would fry the processor...

    Not quite so direct as


    But something that basically did that when executed--probably an assembler instruction.

  • by FreeMath ( 230584 ) on Thursday October 05, 2000 @03:56PM (#727535) Homepage Journal
    $100! Now that's inflation.
  • They were the days...I was working for the local (oz) Sinclair importer; we had to take thousands of ZX80s apart to replace the UHF modulators with VHF (AU Ch 0 and 1) units as the marketers didn't think that the market would spring for new TV's (UHF TV hadn't been around long for us) The computers came to us ready assembled..The cassette interface was a crock..very touchy.
  • by Anonymous Coward
    It would have been a common clock, based on a single crystal divided by the custom IC. The problem was probably due to malfunction of the glue or the ROM when overheated. In those days most systems with any amount of display RAM used either Motorola's 6845 for display timing generation (interleaving bus cycles with CPU access); a few did DMA during the whole scan line but this had heavy CPU performance penalty; others were asynchronous with separate display RAM but this was prone to snow during display updates. The really cheap systems with minimal RAM typically generated an interrupt at the horizontal sync and executed a string of NOPs (either via ROM or bus-pulling); video data was then snooped off the RAM while the CPU walked through a dummy address range. ZX81's glue logic did this. Don Lancaster described the principle very early on in his famous TV Typewriter Cookbook. Who did it first I can't remember, but this kind of trick was common in many of the early video games which often used hw or sw in unorthodox ways.
  • on my way to take the dust off to my Flight Simulator cassette!!
  • This will look great on my horse and buggy! Now if only I could find that "fire" invention that everyone was talking about...
  • I hate to do this to you guys but:

    I had the expansion case, 32K, floppy, 300 baud modem, speech synth, Gorilla dot-matrix printer, and the FORTH compiler! Hah!

    I had more fun exploring different way to program the thing than writing the programs themselves. The sprites on Extended Basic were great. A friend and I wrong a stupid program called Fred and Ed. The equivilent today would be Itchy and Scratchy. Fred and Ed took turns killing each other. One day I gave Fred a bow and he shot Ed in the head with a great explosion of small red sprites. Early carnage. Too cool.

    Anybody ever heard the voice in the Atlanta airport shuttle many years back? The voice sounded _exactly_ like the 99/4a speech synth.

    I, too, regret throwing mine away.


  • For crying out loud, it takes one bit in, one bit out, and a couple of transistors & resistors. *presto*, rs-232. There was even one that just plugged into the game paddle port on the Apple II.

    And if memory serves, you needed the expansion unit on TRS-80, and even then, it only gave you room for a card for rs232, not the actual port.

    Unless, of course, you're talking about much later models . . .

    And isn't $99 a bit steep for one of those these days?

  • As others pointed out, it hasn't dropped in price much! The kit was $99 when I ordered it.

    However, I have slight modifications:

    1) I taped the 16kb RamPack down with black duct tape, to eliminate fear of Ram Wobble. People who whine about this are just not inventive.

    2) Someone said they thought the ZX-81 was POS and replaced it with a TI99/4a. How appropriate then that I used a scavanged TI99/4a keyboard to replace the original contact keyboard!

    Also, I won my first computer contest ever (in KPower magazine), by writing a crossword generation program for the ZX-81. My Prize? A brand new Timex Sinclair 2068, which my parents had also thought to buy for me a week before!! I still have one new in a box.

    Therefore I hail the ZX-81, as it started me down the long and happy road of programming.
  • I can remember some Z80 opcodes as well.

    C9 was RET. ED B0 was LDIR. 01 was possibly LD A, x.

    I havn't touched any of this for 13 or so years, and even then I used an assembler. My assembler was broken with respect to the IX and IY instructions, causing code to be assembled with the opcodes in the wrong order. By the time I'd noticed this the manufacturers of the assembler had ceased trading!

  • Quoted from article:

    You still have the chance to purchase that Timex Sinclair ZX81 computer... Now let's see if we can load Linux on them!

    I wanna buy a couple of hundred and make the world's slowest Beowulf cluster!

    I wonder if it's possible to underclock 'em, or if that would completely screw up all of the IO timing.

    Anyone wanna port the SETI@home client to a Z80?

    Uhhh... How do you mount a cassette recorder onto a Linux filesystem?

  • Also speeds up running the code, as keeping it pre-tokenised means the interpreter has a _lot_ less to do. No need to work out what each instruction does, or to check if they're valid.

    When you get used to it, it's really rather fast to use.

  • It's alot more fun than it sounds. Sometimes you get some downright surreal stuff. Sometimes you get a whole conversation, because the machine didn't stop recording when someone picked up the phone. I have one where some old guy is talking to his buddy about how his wife and her friends are eating all the damn food. The next message was from his doctor about his colon operation apointment. Nutty, Man....

    I have an old Compaq 386SX notebook. Believe it or not, it runs Windows 3.1 and Thought Communications FaxTalk Messenger and an external voice modem really nicely. Connected to my home LAN through a parallel port LAN adapter, it's been a great answering machine for a couple of years now.

    So, of course, you always get the collection of dumbass telephone messages. I save them in a folder on my hard drive and play them every now and then for fun.

    I'm seriously considering putting them up on the 'Net as a shrine to stupidity. Do the same, with yours, it'd be a fun site to go to!

    For legal reason, tho, I suggest that you get a Tripod free page or something and don't give them any real info about you - that way, if the old owner of the machine happens to find them, they'll have a hard time sending lawyers after you.


  • They sell a book on the site - something like "The INS and OUTS of the ZX81" or something. It has a full schematic, as well as interfacing info (or at least that is what the writeup says).

    I support the EFF [] - do you?
  • I had one given to me several years back - of course, it was already put together. I think before I would spend $100 on one of these, I would buy a PIC stamp kit or something.

    But you know how nostalgia is...

    I support the EFF [] - do you?
  • I find it hard to believe what they are asking for these machines. Sure, they are new surplus, possible still in the original boxes, so that has something going for them. And they are arguably worth it as a computer kit. Plus, there is always the nostalgia factor...

    I can understand wanting to buy one to learn more about how a computer is actually built - learning about microprocessors, bus interfacing (for RAM, ROM and peripherals), and digital electronics. There aren't many kits out there that would let you do this at that price, and none as simple, I would wager. I find it strange that someone would want to use these as microcontrollers, though - as it would be cheaper to buy Basic Stamps, or for the assembler freak, PICs (and these are real cheap - $5-6 each). Not as much memory, but much more compact.

    I am reading a book right now call "Build Your Own Self Programming Robot" (I think that is right) by David L. Heisserman (sp?) - about a building a robot he calls Rodney (he has another book, which I may have the titles mixed up, about a system named Buster - Buster came before Rodney). The systems computer is built around an 8085 microprocessor, and a bit of RAM chips, and a bunch of glue logic. Data is entered into the system via toggle switches - one bank sets the address (12 bits), and the other bank the data (8 bits), then there are toggles for load, reset, and run/program. It is pretty clearly laid out.

    I gave thought to actually building this thing, as diagrammed in the book, but after reading about it, I realized that most of such a system could be built using a cheap 486 laptop (which I have one with a busted screen) and the parallel port, plus a little bit of addressing logic on the parallel port. Then some custom coding, and there's Rodney. Still, it was fun reading that 80's robotics book, and realizing how far we have come, yet how so far we have to go (the books author was real optimistic about robots and what they could/should be able to do)...

    I support the EFF [] - do you?
  • EMI? That's sort of unlikely for stuff running at low speeds and for circuits of that size. More likely it's a power supply problem.

    Nope. The power supply was stiff and well filtered, and separate for both the motors and CPU. The motors were isolated from the CPU by relays (with the proper reverse EMF blocking diodes). Small DC brush motors put out a *lot* of noise, and apparently the ZX81 was pretty susceptible. The ZX81 put out a *lot* of noise itself, too, especially when I ran it without a case. but the EMI problems I had were there with or without the case.
  • Actually, the ZX81 could work with up to 64K memory (minus the 4K ROM). I know that for a fact, because my dad built a 64K ram pack for mine.

  • Right, so you have 1024 bytes of RAM, but part of these are used for storing environment variables.

    From (my chemical) memory, the ZX81 Memory map looks like this:

    Decimal address 0 to 8191 ROM
    Decimal address 8192 to 16383 Copy of ROM (this can be overlaid by a second add-on ROM)
    Decimal addres 16384 upward is RAM.

    Addresses 16384 to around 16515 (Im' guessing the figurse a bit now...) stored the environment. This means things like the lines at the bottom of the screen that are reserved for editing, the "protected lines". These don't get scrolled or cleared by a CLS command, so you can use them for stuff like status, background. Another address contains the number of TV lines before the picture starts. If you POKE a value into this address, you shift the whole display up (or down). I used this once for an earthquake effect, by vigourously drawing a skyscraper, shaking the screen, then drawing a pile of rubble (OK, I was 12 at the time).

    So, you've really got less than 1024 bytes for your program and data! Oh, and the screen is memory mapped into that space, too! You had a choice, limit the amount of screen you used, or limit the size of your program. The screen works like this, each line is mapped as a series of characters, teminated by a newline character. If you never print to the screen, the screen memory stays fixed (perhaps at 1 character, a single newline). If you print


    , you're going to gobble up 68 (if I've counted right) bytes of memory including the two newlines.

    Now, the Basic keywords were part of the character set, so for example the keyword PRINT occupied only one byte. So you could economise by using these basic keywords to print text to the screen. For example, to prompt the user to type a number, you could use the keyword INPUT (1 byte) rather than ENTER (5 bytes, including the space). Big saving.

    More memory could be saved by doing numerical operations on the values of strings, rather than on numbers themselves... doing (the value of letter "A" plus the value of letter "B") took up far, far fewer bytes that (64+65).

    Then if you programmed directly in machine code, you could do wonderfule things... Two lads from Hull (U.K.) set up a firm called Artic; they managed to cram a game of chess into 1kB!!!!

    We used to use these things at school, too. An I/O card plugged into the expansion bus, a few relays, and we could play around making traffic light systems, reading temperatures and light levels, turning on pumps to sprinkle water on the plants...

    Those were the days! All you need is a bit of imagination. Oh, and it was small and ran silently, no annoyingly noisy fans and hard drives....

    It ran from a 9Volt transformer, too. 700mAmps, I think. You might be able to run it off a PP3 battery...

  • I've archived my old MITS Altair sw eariler this year and found that MP3 worked great with the 88-ACR. It stores data using 2400 and 1850Hz at 300 baud. Dunno about the ZX81 audio format (I bought one of those from these guys before they raised the price to $100 - it was around $40 a couple years ago, heheh. Haven't even built it yet tho).

    BTW - saving old computer audio data with a PC sound card, preferably just make an audio CD, is HIGHLY recommended as you won't have any of the tape problems of noise, hiss, drop outs and speed fluctuations, is much more reliable - and those old tapes aren't getting any younger you know. After a time the lube dries up and then you'll have a problem with it squealing and that definitely throws a monkey wrench into loading 8K BASIC.
  • actually if i remember correctly the zx81 had more like a 40x20 screen without colors at 8 bit a character that would be 800 bytes.

    It actually used a neat trick to vary the size of memory used by the screen. So that largish programs could fit into the 1K unexpanded version.
  • 5. most people NEVER erase the tape before giving it to goodwill, so now you can go home and listen to peoples messages.

    Damn, I'm glad I only use digital answering machines at home! I hate analog tape formats because they have crappy quality, and the hardware is unreliable.

    This sounds like more fun than what I like to find at thrift stores, which is old Mac hard disks and Syquest cartridges. One time I found a backup tape from a SCO Unix system, and a tape drive that could read it. Nothing really fun, though.

  • Save your money, build one from off the shelf components:

    http://www.home-micros.fre ese []

  • by localman ( 111171 ) on Thursday October 05, 2000 @08:59PM (#727614) Homepage
    Just be glad no one mentioned putting together a beowulf cluster of them.



  • by TheGratefulNet ( 143330 ) on Thursday October 05, 2000 @04:01PM (#727621)
    you can hook it up to uhf channel 33?

    uhm, will they sell me a 70's era tv that has UHF channels still on the "dial"?

    I started off with the trs-80 model 1, so while I'd like to own one of these for memory's sake [sic], there's no friggin way I'm paying a c-note for a chip that can't even be given away (the z80).

    and I bet you'd have to take steel wool to the pcboard since its probably tarnished beyond all believe from oxidation.


  • You too can live in time when men were men and sheep were scared.

    Put together your own computer and watch that BASIC fly. For only 99.95, you can own a piece of history and have a truly 3l337 paperweight. "I built this wrong all by myself."

  • As it has always said in my User Bio (not altered for this article), I probably owe my career and geekhood to my ZX81, 16k RAM, and B&W TV that I bought for $210 all told with my paper route money. My folks thought I was nuts at the time, my wife finally convinced me to throw it away in the early '90s, but that machine was how I learned BASIC and Assembler in a neighborhood where no one else had a clue.

    And, yes, it was a horrible POS, but I would have been another 5 or more years behind without it, and a more usable machine wouldn't have taught me half as much.

    So there!
  • by SydBarrett ( 65592 ) on Thursday October 05, 2000 @09:21PM (#727628)
    The easy BASIC of the TI99/4a got me into computers. You could do text to speech with the speech synth and the Terminal Emulator 2 cartrage. You went into "BASIC" (which the TE2 cart modified in some way) and do something like the following:

    10 open #1,(some link to the speech synth, forgot what it was)
    20 print #1,"Hello! blah blah blah"

    How more easy can you get? you could modify the speech by doing something like this (not sure of the syntax):

    30 print #1,"\\50 40"

    The first was the pitch, and the second was the rate the tone would drop as it spoke. You out really high/low values and get crazy disorted voices out of it. Good for making prank phone calls. :)

    I even had the PE box (extra 32k,disk drive,rs-232,cool blinking lights), but the stupid extra thick cable always kept falling out of the bus port. The Extended basic cart let you do hardware based sprites, which looked way cooler than moving a character block by block.

    Games? Parsec, of course. Remember trying to re-fuel by hitting '3' and steering in the narrow tunnel? Had most of the Atarisoft games, Tunnels of Doom, some infocom games (HHGG, still have the "Don't Panic" button), and other stuff. I used TI-Writer to do all my high school papers, and had to send escape codes directly to the printer to do underlining (good thing TI-Writer supported that trick). Even had TI-LOGO, that let me play with simple recursion. Of course, by the time I got all this stuff, it was dirt cheap.

  • SLOW could be simulated in software on the ZX80. It took about 400
    bytes of code (half the default size of the RAM :->) but it worked
    well enough. There was even a commercial game released that used
  • by /dev/kev ( 9760 ) on Thursday October 05, 2000 @04:05PM (#727633) Homepage
    Now let's see if we can load linux on them!

    Ugh, must EVERY story mention Linux? I mean, I know we like Linux and everything, but mentioning putting it on a 4.77MHz Z80 just makes me feel sick.

    What would be an otherwise excellent nerdy retrocomputing story is tarnished by the ObLinux mention. Can't people just appreciate this stuff for what it is?

    I'll say it again, ugh.
  • by Dr. Evil ( 3501 ) on Thursday October 05, 2000 @04:05PM (#727637)

    Just remember how little you can squeeze in there. Your program and data have to fit in 1024 bytes... unless you get the memory pack.

    A PC 80x25 character screen is 2000 characters.

    I bought one of these at a garage sale for $15CDN when I was in gradeschool. It was so cool.

    I think that exhausts all I have to say about the machine.

  • by SydBarrett ( 65592 ) on Thursday October 05, 2000 @09:31PM (#727638)
    "Anybody who pays $99.95 for these is -- excuse me -- a fucking moron."

    If it wasn't for morons, Ebay would not exist. :)

    Thank god for Goodwill and Value Village, it's where I get most of my clothes. Got a SGI/Cray T-shirt there for $1.00.

    And now, as a service to the Bored Slashdot Reader...

    The best thing to do at a Goodwill is this:

    1. go to a goodwill
    2. look for some used answering machines
    3. take the tapes out
    4. take them to the checkout, the chasier will just make up some price
    5. most people NEVER erase the tape before giving it to goodwill, so now you can go home and listen to peoples messages.

    It's alot more fun than it sounds. Sometimes you get some downright surreal stuff. Sometimes you get a whole conversation, because the machine didn't stop recording when someone picked up the phone. I have one where some old guy is talking to his buddy about how his wife and her friends are eating all the damn food. The next message was from his doctor about his colon operation apointment. Nutty, Man....

  • The Z80 processor finds its home currently in a far more compact device: TI Graphing Calculators. I have seen these controlling all sorts of things: infrared transmitters, light displays, and an affordable combination between educational calculator, and gaming machine.

    The TI-83, the most popular one, retails for about $100, but is smaller, uses only 4 AAA batteries, has a serial port, and can be carried around in a pocket to show off your geekiness. Still, you could use the Sinclair ZX81 as sort of a base station, or one with an AC adapter and TV out. But never underestimate the utility of a programmable Z80 graphing calculator.

    Tell me what makes you so afraid
    Of all those people you say you hate

  • Hey, I've still got my "fat" 4032 packed up in the basement along with a 8050 floppy drive. When is the Linux/FreeBSD crowd going to get their act together and do a port to some serious 1 MHz hardware ?
  • by joshv ( 13017 ) on Thursday October 05, 2000 @04:07PM (#727644)
    When completed, the ZX81 computer can hook up to UHF Channel 33 on any black & white or color TV for its video display (U.S. NTSC Compatible).

    Oh man, that's UPN where I live. There goes Moesha...


  • Wow, this was the computer that started it all for me. My parents purchased one for me when I was the grand old age of eleven, and I guess it all went downhill from there :) I still remember purchasing the 16K RAM pack for it a couple of months later, and being completely frustrated at the fact that if you pressed the keyboard too hard the RAM pack edge connector would flex and cause the machine to crash. I tell you, it's amazing what a liberal application of epoxy resin can fix :)

    Anyway, enough of my misty-eyed reminiscing and on to my real comment:

    Has anyone ever over-clocked one of these babies? I'd love to see how fast some psychopath could get one going with some extreme refrigeration / cryogenics thrown in!

  • Linux was created initially targeting the 386 (much to the consternation of Professor Tannenbaum) but that was then, this [] is now.

    Now hiring experienced client- & server-side developers

  • by kzinti ( 9651 ) on Thursday October 05, 2000 @04:07PM (#727652) Homepage Journal
    I remember ordering and building my Sinclair back before Timex became involved and it became the ZX81. Wow, what a memory trip it is to think about putting together that thing... I can almost smell the 60/40 now.

    Unfortunately, I never got to do much programming on mine... it had a temperature problem. After a few minutes of running, the TV would lose horizontal sync. Turned out that my ROM chip ran way too hot, and as it warmed up the TV signal went out of sync. Sinclair must have saved money on components by interleaving the sync of the ROM with the video generator, instead of having separate clocks for each. My girlfriend's techhead brother figured this out for me -- never would have discovered it on my own.

    We solved the problem by keeping a piece of ice on the ROM chip, in a little plastic bag. Every so often, when the ice had melted, I'd have change the bag for one with a fresh piece of ice. Talk about your cooling problems -- and I wasn't even overclocking!


  • The damn RAM pack was the worst POS I ever saw. After a few hours plucking away at assembly language, one false wobble would make the whole thing crash (hmmm, is there a RAM pack in WindowsÉ heheh).

    It things like this that epoxy resin was invented for :) I'm not kidding - the join between my ZX81 and 16K RAM pack looked like Ridley Scott's Alien had built a nest around it!

  • Anybody ever heard the voice in the Atlanta airport shuttle many years back? The voice sounded _exactly_ like the 99/4a speech synth.

    I allways wanted to hack that (the airport shuttle, not the 99/4a) to say 'By your command'.

  • Ah ... the memories it brings back ... this was my first computer. I learnt to program in BASIC in the ZX81. If memory serves me well, the BASIC manual that came with the machine was an excellent book. And who can forget the dodgy 16K RAM extension pack? One slight wobble and all your hard work will be gone ... I never managed to get the cassette recorder to load stuff, so I had to type in all the games from scratch ...
  • i know this site for years, and last year the kit was 29.95$ or 39.95$ i'm sure of that!
    i built my first ZX81 at 12 y/o with my father, in 1982, and this is on the ZX81 that i learned BASIC and assembler, pretty cool machine! it still working, have a bunch of wire outside now, to connect a joystick, and some I/O port. This is the machine you can build a lot of hack, 64Kb memory, color, sound, graphics, etc.
  • Linux is amazing and I'm a fan of putting it on everything, but I doubt you'll have much luck putting on a machine with just 1K of RAM!
    The TS1000 computer has 2K of random access memory built into it. (The ZX81 has just 1K.) The Sinclair 16K RAM Pack will increase your computer's memory capacity to 16K so that you can load and run all of the most popular software titles. This 16K RAM can also be used to extend the TS1500's built-in 16K RAM to 32K.
    For comparison, I run NetBSD on my Workpad z50 [] but I have 48 MB of RAM and a 96 MB CF card.

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  • The off your geekiness...

    Why would I show off my geekiness with a crippleware calculator that can't even type a lowercase character? The TI-83 is deliberatly crippled to be aimed at high school... which makes me shudder to think they're using them in college classes here. Anyway, the TI-86 is better for most stuff.

  • "I had a few and thought that they would make a pretty good controller board with the Z80 processor. Now let's see if we can load Linux on them!"

    Yeah, right. The Zilog Z80 was the first Intel PC processor spoof, and is the same exact processor which is in the TI-82, 83, 84, 85, and 86 graphing calculators. Now those models take an incredibly long time to draw a circle with a resolution of 5 degrees (about 30 to 50 seconds; I own a TI-89 now [10MHz 68000], so I don't exactly remember). Can you imagine how long it would take to have the 8-bit SCSI card do a hard disk scan?

    In short, if you want a geezer for Linux, I'd recommend hunting for an old Dell OptiPlex; those usually have some good chipsets in them (I found an old XM 590 with the Intel Neptune chipset, popped in the Pentium OverDrive, squeezed in RedHat, and it worked; probably a hell of a lot better than that Z80 fossil of your affection).

  • The thing worked, and the 6502 still is the hallmark of 8bit CPU design to me. Z80 is sort of ... ugly.

    Yeah, all those extra registers hanging off everywhere truly screwed the aesthetics into the ground. The 6502, with it's sleek and aerodynamic 6 register design, really set the style for future processors.

    (BTW, I'm not harassing you - anyone who owns a 2001 is cool in my book. Didn't that thing show up on Battlestar Ponderosa on a regular basis? Or maybe I'm thinking of Buck Rogers... with Erin Gray in spandex it was hard to concentrate on the background...)
  • How much did those bad boys cost in 85? I like to collect old machines, but my price limit is 25 bucks.

    If anyone wants to pick up a very cool old computer, get a hold of a Tandy 100 or 102. It's a portable computer about the size of a dictionary that runs on 4 AA batteries for a month. I used to keep addresses and phone numbers in a 102 at school. You get some really great looks when you pull out a 15 year old computer in a EE class to get someone's number.

  • by fudboy ( 199618 ) on Thursday October 05, 2000 @04:13PM (#727673) Homepage Journal
    a lot of folks are going to wax nostalgic over this here machine, but I'm gonna have to disagree. This was my first computer. I recieved it IIRC around Oct 1982, and I was stunned at how crappy a machine this was. I was 9-10 years old, personal computers were an utterly and completely brand new phenomenon, but I could immediately sense the uselessness and cheapness of this machine.

    My dad, who bought it for me, had previously engineered some of the first networked cash register systems in the mid 70's (for the Burger Chef chain of fast food resturants), he was/is a primordial hax0r, but even he couldn't get into this dog. But he could understand my dismay, so he got me a TI994a.

    I would love to get a bevvy of brand new TI99 parts, maybe even c64 or some '086's, but I can't quite bring myself to embrace this amazing find.

    just my $.0200251

  • I love this testimonial:

    from a NASA engineer .." send me four more kits, I'm using them as controllers for a project"

    Oh boy, here we go again...
  • You get some really great looks when you pull out a 15 year old computer in a EE class to get someone's number.

    Think of all the girls you could get with one of those. And most geeks are still wondering why they're still single.

  • eBay is your friend:

    ZX81 For Sale []
    (and others)


  • Anyone wanna try Dunking one of these in flourinert [] and see if ya can't push her up to 500MHz?

  • Another way of looking at the Z80 is sort of like a 286, only faster.

  • by tgeller ( 10260 ) on Thursday October 05, 2000 @04:33PM (#727716) Homepage
    Anybody who pays $99.95 for these is -- excuse me -- a fucking moron.

    I was at the Vintage Computer Fair [] last weekend, and the going rate is about ten bucks. Yes, with manuals and everything. My VIC-20 isn't even worth a quarter of that price, and that's including the original boxes, manuals, an expansion card, programs on tape, and a bunch of other cool original stuff.

    By the way, the original price was... $99.95! (Oh, O.K.... they started out at $199.95, but were later lowered to $99.95. I last saw a new one in a store in New York City in the late 80s for $14.95.)

    This link [] may be of interest to the ZX-curious. --Tom

  • I plan on loading linux on my penis, maybe that stupid bird will stop crashing.
  • Heh. Nice DeVo play in the .sig there, my friend.

    For the record, I have no idea what kind of Sinclair the first computer I ever used was, but I remember it as a Timex-Sinclair 2000. It had a chiclet keyboard and I used to plug it into a small black and white TV and write BASIC programs, mostly Mad-Lib type things and random pattern generators (the easy kind you can make with "10 print something stupid, 20 goto 10". My friend had a tape deck and we managed to waste alot of time typing in stupid little programs like one that gave you an ASCII-graphics drawing of dice and randomly "rolled" them for you, and then saving them onto tape cassettes and loading them back in. Woohoo.
  • If you look up ZX81 on eBay, there's another auction for two of them, all in pieces. So you have a choice :-).


  • by fm6 ( 162816 ) on Thursday October 05, 2000 @04:39PM (#727725) Homepage Journal
    A better-known example of a current Z80 product is the Gameboy. Plus there are a zillion controller or embedded systems.

    This chip is a definite classic. Has any instruction set been in use as long? Indeed, before IBM jumped into the microcomputer market, Z80-based systems were the standard for desktop business computing. And probably the most popular config was an Apple ][ with a Z80 coprocessor board. (I once nearly bought the Microsoft version of this one!) If Apple had known how to exploit its dominance in this market, history would be very different.

    I just went to the Zilog web site to see what they were up to, and found the latest Z80 product: an embedded web server! []


  • by tokamak ( 240646 ) on Thursday October 05, 2000 @04:41PM (#727726)
    I've just installed linux on my bodylotion box and I am creaming it all over my body.
  • Title says it all... run Linux? I think it has 1k of memory unless you get the memory pack which gives you a whopping 16k, and make sure you don't jiggle it or the system will crash.
  • If you want really neat hack value, try building one of these puppies from scratch. Perhaps somebody could make a really nice high-res scan of the mainboard of this thing. I seriously doubt if the board is multilayered; you could probably build an equivilent machine yourself on a breadboard. It was a cheap POS when it was new; even paying rat shack's inflated prices for components you could probably build one for
  • There's no way I was implying that they could cram that much text onto a television display. A C=64 could barely do that.

    The ZX81 did something weird with the programming language too. It was BASIC, but the way statements were constructed made me think that they were not relying on the characters to make up statements, but on the order of character sequences.

    I.e. A couple characters for a line number, a single character for a command (goto, print, for, DIM etc) another single character for the parameters for that command, or several characters for a line number.

    If that is not how it was stored internally, it certianly was how you would program the thing.

    My comment on how little 1024 bytes was only to emphasize how terribly small that was.

    Gawd... I remember noticing all these strange things for the first time... somewhere in a New Brunswick campsite with an extension cord, a picnic table and a black and white T.V.

  • I still have my Timex Sinclair, that we bought in 1982. It sports the following:

    - 2KB RAM
    - 150bps cassette interface
    - 16KB RAM Pack
    - 32 column printer

    The damn RAM pack was the worst POS I ever saw. After a few hours plucking away at assembly language, one false wobble would make the whole thing crash (hmmm, is there a RAM pack in WindowsÉ heheh).

    I also remember doing some BASIC on it. The computer would refresh the entire line you were typing at every character. For the first 32 characters this was fine, but after 2-3 lines, typing became utterly sloy, hence the "Fast" button.

    In any case, this gem got me started on computers. I still have the original box and booklet. History in the making!!
  • The problem with the game boy/pocket/color is that there is no easy way to load a program into it short of burning a cartridge. The TI-73/82/83/85 have a serial port that allows the user to download a basic or assembly program into the calc's onboard memory of about 300K. This is why [] has hundreds of user-created programs for each calc TI makes.

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    Of all those people you say you hate

  • Don't forget the color gameboy has 2 Z80's. One for pixels, and one for color :-)

  • In '85? They were already pathetic has-beens even back then. I remember me and my buddies used to self-rightously look down on these and laugh at 'em in '83. I was soooo glad that my parents got me a Vic20 instead. ;-)

    Although the VIC was it's own kind of hell, at least the screen didn't start to shrink as it ran low on memory.

    In the late 80s I saw an ad in the paper, some old geezer was selling a pair of them for 20 bucks, with 16K RAM expansions. Actually, one was a ZX81, and the other was a TS1000. I bought 'em and gave one to a friend for a laugh.

  • by Matt_Bennett ( 79107 ) on Thursday October 05, 2000 @05:34PM (#727743) Homepage Journal
    I had a few and thought that they would make a pretty good controller board with the Z80 processor.

    I did a project in high school (~1985) trying to use a ZX81 as a controller for a robot. It worked, kinda. Very susceptible to emi, especially the sort that small DC motors put off. It used technology that was "good" for the time, which translated to today's technology, means "slow and power hungry."

    Other than the "vintage-cool" factor, as a controller, you can do a whole lot more with a modern microcontroller. More I/O, similar amount of memory, much more in terms of MIPS/W. You do lose the video display and the ability to program it in BASIC.

    The ZX81 was a great hack. The ability to implement a GUI (it did output to a TV) and an interpreter with that little amount of processing horsepower, RAM and ROM is a pretty impressive feat, especially keeping it relatively cheap.

    I think that we could all learn something from the ZX81- it is amazing how far you can stretch your resources when you don't have many. The real power of such knowledge is knowing when it is appropriate to use it.
  • by DigitalDreg ( 206095 ) on Thursday October 05, 2000 @04:51PM (#727748)
    I still have my original TS1000, which was my first computer at the age of 12. I picked up another one for parts later on. The TS1000 was the Timex/American version of the ZX81, a product of "Uncle" Clive Sinclair. It's notable features where:
    • BASIC in an 8KB ROM.
    • 2KB RAM on board
    • Expandable to 16KB RAM with a "backpack"
    • Expandable to 54KB RAM max with some mods.
    • A 40 key keyboard with multiple shift modes to get all of the characters and BASIC keywords.
    • Cassette interface for program loading and storing.
    • A low cost thermal printer.
    This was not a serious machine; it had major shortcomings. But the price was right.

    The keyboards were very troublesome. The thin ribbon connector often cracked from the heat and aging, disabling the membrane keyboard. With a little experimentation you could still "pick" it with wire ties. ;-)

    The cassette interface was flakey too. They recommended a mono portable cassette recorder, run from batteries. The volume level had to be "just right."

    The memory backpack was troublesome as well - it wiggled too much, breaking the connection to the card edge connector on the back of the machine.

    Entering programs on this machine was truly unique - you didn't type the word "PRINT". You pressed "P", and depending on where you were on the line, the BASIC interpreter knew if you were going to enter a keyword ("PRINT"), or if you wanted the letter "P". Sorry, uppercase only.

    It was amazing was assembly language programmers could do with this thing. I fondly remember the Flight Simulator, which fit on a 16KB machine. There were programmers toolkits on cassette, and other little applications. Data storage was a serious problem though.

    Is there an archive of ZX81 software anywhere, possibly in WAV or MP3 format? I still have my cassettes, but after 16 years of disuse I doubt that they are readable.


    PS: Search on google - there are several projects out there for emulators.

  • I've still got both of my TI99/4A computers, and they work great. I've got both the standard beige model, and the black/chrome one. I've even got the speech synthesizer attachment! Ahh, the days of playing Parsec, Hunt the Wumpus, and Slymoids come back to me now...

    The stupid adapter to make Atari 2600 joysticks work with the thing rarely functioned, I usually wound up not being able to move my guy in one direction or the other, but I mastered the keyboard controls. I think I still have the tape recorder and necessary cables to hook that up, then you could actually play BIG games that loaded from the cassette tape.

    I had a big book of BASIC programs that I messed with, actually learned quite a bit about programming BASIC just from playing around with those, but the machines have sat under my parents' and grandparents' basement TV's for about 10 years now, neglected and gathering dust. They're right next to the pong machine...

    I never knew anyone who had one of those, besides myself, everyone had C64's...
  • Hemos isn't the one who suggested Linux on this thing... Eugene Blanchard did.

    Just making sure you ain't slamming the fine folks at Slashdot (there's my suck-up comment)

  • You could always use virtual memory....
    ...on a standard cassette tape!

    I had forgotten that option...

    That reminds me of the Apple documentation that came with my Apple ][+ (in 1979, IIRC). In the section on using the cassette tape storage device it made reference to the amazing abilities one may possess if he could understand the program code whenthe tape was played through a speaker. Needless to say, I spent a couple hours trying to figure out if I had such abilities...

    Hey, I was 13!

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  • how many times I retyped a program because I bumped that 16k RAM pack and lost it all....

    There were too many times that happened to me, so I soldered the ram pack directly to the back. That, and adding more aluminum to the voltage regulator heat sink made it very reliable. Things were great until I developed larger programs enough to notice anything greater than about four kilobytes would freeze. Turned out there was a bit stuck on a 1 in RAM about 4K in one of the chips. RAM was expensive back in those days. It cost me $49 for 16 kilobytes (and that was cheap!)

    I got a lot of use out of that little computer [].
  • The cassette interface was flakey too. They recommended a mono portable cassette recorder, run from batteries. The volume level had to be "just right."

    yup, like the old trs80 model-1 thru 3. before we could afford those expensive 5.25" floppy drives, us kids who owned the trs has to live with about 600baud over cassette tapes via the analog out. and the volume was pretty critical or the load would be bad. and you'd only find out the load was bad after you attempted to load the whole program or data file and found the cksum was bad ;-( this could be as long as 5-15 minutes of realtime cassette/data playback.

    I remember building a PLL front end box that would follow the zero-crossings and retime/relevel the waves so that the computer's analog-in would be happy. sort of an analog compressor. sort of.

    and to add to all that trouble, there was NO transport control. you had to press PLAY and then STOP when the display told you to. and if the load was bad, you had to REWIND the tape and start all over again. and write down cassette 'index counter' numbers if you dared store more than one item per tape. don't forget to leave at least 10 seconds of leader between each section; especially since the 'seek to next object' was accomplished by PLAY+FF and listening in the speaker for the 'noise' to silence. we even joked about creating a musical band and calling it c-load .

    uhm ... z80-based computer from the 70's ... no thanks. I can't even imagine living with floppy disks (as the primary and fastest storage) ever again. forget that craziness of having to load program data over 600baud analog cassette tapes! brrr!!


  • I make a hobby out of going to surplus stores and picking up surplus hardware real cheap. I've got all sorts of crufty old stuff, none for over 15 dollars. They were selling VIC-20s and C-64s for $50. This is way too expensive, and even though it'd be a nice little piece of hardware to have, it's too expensive and not worth the price they're asking.

    Let me put it this way. I picked up a drawing tablet that works with mouse protocol for $15. I picked up a much more recent, in fact, brand new, microcontroller-based device that only needs reprogramming for $5.

    That price is outrageous. Wake me when they sell them for $10.

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