[HN Gopher] The ZX81 Turns 40
___________________________________________________________________
The ZX81 Turns 40
Author : ggambetta
Score : 119 points
Date : 2021-03-07 07:53 UTC (15 hours ago)
(HTM) web link (www.theregister.com)
(TXT) w3m dump (www.theregister.com)
| j11m wrote:
| My grandfather, who worked in electronics and ham radios, bought
| one of these. He didn't care for programming and gave it to me.
| "Here's the computer, the manuals, the wires and a black-and-
| white TV. You might like this. I didn't."
|
| I grew up in a modest-income household and didn't get a lot of
| good guidance from my parents. My dad literally told me that I
| should not learn to work with computers because they would "think
| for me".
|
| I learned it despite my father. I consider his hand-me-down gift
| as one of the most significant gifts in my life, as building
| computer software has been my career for over 25 years.
| rwmj wrote:
| My first computer - I still have it although it needs
| restoration. We didn't know at the time it was so limited because
| there was nothing to compare it to.
|
| The author of the programming manual - Steve Vickers - could be
| thought of both the first and last person to formally teach me
| computer science, since I eagerly followed the entire manual back
| in 1981, and then 15 years later I took his notoriously difficult
| and impenetrable course on Mathematical Structures at university.
| amelius wrote:
| I grew up on the Apple ][ but I can certainly relate to some of
| the stories here.
|
| Except now I hate Apple for turning into such a snob company :(
| Theodores wrote:
| Imagine a Sinclair laptop. With options for a monochrome screen
| and a flat membrane keyboard. There would be no internal
| battery, just a wedge shaped power brick. The case would be
| black. RRP? 99.99
| nickt wrote:
| The Z88 came pretty close to that, though the keyboard was
| better. It's 34 years old, wow.
|
| https://en.wikipedia.org/wiki/Cambridge_Z88
| sys_64738 wrote:
| I have a Timex Sinclair 1000 in my basement (the 2K USA version
| of the ZX81). Commodore had the largest warehouse of these in
| North America by 1984.
| nickt wrote:
| > Commodore had the largest warehouse of these in North America
| by 1984
|
| That sounds like a story, have any more details?
| TMWNN wrote:
| sys_64738 is referring to Commodore running a tradein program
| for $100 off a C64 with any computer or videogame console.
| People purchased the Timex Sinclair for $45 solely to trade
| in (https://dfarq.homeip.net/wp-
| content/uploads/2020/08/timex-co... supposedly, Commodore
| used them as doorstops.
| nickt wrote:
| Thanks! I had no idea.
| sys_64738 wrote:
| The C128 from 1985 had a Z80 built into it. Where did those
| come from I wonder?
| timbit42 wrote:
| Bil Herd claims he took the Z80 used in the prototype
| C128 from one of the ZX81 doorstops.
| nickt wrote:
| Great point. I just had a look in my C128 and they are
| just regular branded Zilog Z80s. I sure there's a story
| there too...
| elvis70 wrote:
| First computer of the family, received as a kit. My mother, my
| father and I took turns copying listings from books and
| magazines. I remember we were very enthusiastic and fascinated by
| this machine. The first words I achieved to type on it were swear
| words.
|
| My phalanges still remember it!
|
| Having said that, I had an instinct of repulsion at the sight of
| the RAM pack on the photo.
| uncledave wrote:
| Ah the RAM pack. This resulted in a life of wiggle wiggle crash
| crash.
|
| I managed to get my hands on a beeb eventually. Thank goodness.
| steverb wrote:
| This is the computer I learned to program on (the TS1000 US
| Version). The manual for it still has place of honor on my
| bookshelf.
| analog31 wrote:
| I heard through the grapevine that K-Mart was blowing out a
| Timex/Sinclair computer for 30 bucks, so I hopped on my bike and
| brought one home. I used it to program a formula from a book
| about loudspeaker design, to make a speaker for my electric bass.
| My program spit out a bunch of numbers, which I graphed by hand,
| but I was in heaven. (Turns out looking back, I'm pretty sure the
| formula in the book was wrong).
|
| I couldn't get the cassette interface to work, so I begged
| everybody in the house not to unplug the computer until I was
| done with my project. A few weeks later my mom got a Commodore
| VIC-20, which of course had a full keyboard, so it became my
| computer of choice until I finally got a more elaborate machine
| in college.
| nickt wrote:
| In terms of ROI, the best PS69.95 I ever spent (I still have the
| receipt from WH Smith). It wasn't the first computer I ever used,
| but it's the first one I ever owned at age 9 and it led me down
| the path that'll be familiar to many here... I'm glad I still
| have it, and the Spectrum and Amiga's that followed.
|
| Incredibly, the ZX81 hardware and software scene is still alive.
| You can get parts for it quite easily, including keyboard
| membranes, molex connectors for the membranes, replacement jack
| sockets. SellmyRetro is a good place to start [1]. The composite
| video out is a simple and worthwhile modification.
|
| The ZXPand+ interface [2] is an expansion unit that has a 32k RAM
| upgrade, SDCard slot, AY sound, hi-res support and a 9-pin
| joystick interface.
|
| The zx-key is a replacement keyboard, and David Stephenson tells
| a great story about its creation [3].
|
| And games too [4]. I always loved the design of the cassette
| covers, and cronosoft guys have done a great job reproducing
| them. I reminded how good an imagination you needed playing these
| games back in 1981!
|
| [1] https://www.sellmyretro.com/category/retro-
| computers/sinclai... [2] http://www.rwapsoftware.co.uk/zx812.html
| [3] http://www.zx81keyboardadventure.com/search/label/ZXKey [4]
| https://cronosoft.fwscart.com/SINCLAIR_ZX81/cat5357733_41194...
| criddell wrote:
| I asked for a TI-99/4A because that's what my best friend had
| and we would make games and share them with each other.
|
| When I think back to the microcomputers of the early 80's, I'm
| kind of astounded that they sold in the numbers they did. They
| were pretty useless.
| TheOtherHobbes wrote:
| They were imagination amplifiers. The computer itself didn't
| do much so you had to fill in the gaps by imagining the
| things it wasn't doing - often guided by some exciting cover
| art on books and games packaging.
|
| You could also expand your imagination by thinking of the
| things you might do if you worked hard at it, or if it was
| only slightly bigger/faster/better.
|
| Modern computing is the opposite. It does so much it doesn't
| leave any gaps for your imagination to fill - the creative
| equivalent of a distracting wall of noise for you to consume.
| ddingus wrote:
| Great phrase!
|
| In my view, this is one of the appeals very low resolution
| graphics can bring to the table.
|
| Code does not have to do much, which helped the fun alone.
|
| See the blue ones? Yeah, collect those. Reds are baddies...
|
| Or, on a ZX81 or PET, it was just shapes.
|
| Still that was enough. Let the mind run wild!
| nickt wrote:
| > imagination amplifiers
|
| Thank you for that, yes - that explains them perfectly.
| Probably explains why I've always felt more at home in the
| terminal.
| bm98 wrote:
| 1982 Atari 800 here (was 8 years old at the time). I remember
| thinking the same thing at the time. When we first bought the
| thing, there just wasn't much I/O beyond the tape drive (and
| later the disk drive), and therefore the things we could do
| seemed very limited. It wasn't until we got a printer (a Star
| Micronics SG-10 dot matrix tractor feed) and a 300-bps modem
| that the world really opened up!
| rootbear wrote:
| I never had any of the classic 8-bit home computers. I built
| a CP/M system from an Ampro Little Board, connected to the
| Heathkit H19 terminal I put together. The downside of that
| was little commercial software, but I mostly used it for
| accessing the University VAX 11/780. I follow a bunch of
| retro-computing Youtubers now and I feel like I missed out on
| something. My best friend had an Apple II and was always
| suggesting I get one. He still has it.
| neilv wrote:
| The TI 99/4A was great in some ways, especially because at
| one point TI was dumping or loss-leadering them, so, IIRC, a
| family eventually could pick up one for $50.
|
| Though, one of the big drawbacks of it, relative to some
| other home computers of the time, is that you couldn't really
| take advantage of the overpowered graphics processor using
| the TI BASIC that came with it. To use assembly language, you
| needed a rare add-on. IIRC, there was also an Extended BASIC
| cartridge, which was also rare.
|
| But the TI 99/4A wasn't useless -- you could do a lot with
| character set definition and sound from the stock BASIC, and
| it came with a great introductory book that taught you enough
| to get started creating with those. With some creativity, you
| could do a lot with that. (Flight simulator? So long as you
| didn't bank too fast for characters to be redefined for the
| horizon, maybe. :)
|
| I recall the family going to some dingy school-supply audio-
| visual store to look at their Apple computers. They had the
| //c and I think //e on display. Then my parents saw the
| price, and I could tell it was way too high. So, TI 99/4A it
| was, plugged into a portable little B&W TV that my dad bought
| from a guy at work. (Until I made enough money lawn-mowing
| and babysitting and various money-making schemes, and a
| kindly computer store owner gave me what had to be a below-
| cost deal on a semi-compatible PC.) Apple got some pre-Mac
| glory for microcomputer innovation, but I suspect that the
| _non_ -Apple $100-$250 home computers reached more families
| at the time.
|
| Having _a_ computer was infinitely better than _no_ computer,
| and the TI 99 /4A was a good little imperfect computer.
| spongeb00b wrote:
| Even Blu-Tack for holding on the RAM expansion is still
| available to buy (sorry, too hard to resist)
| nickt wrote:
| Real coders use Velcro ;)
|
| [EDIT] actually, the Memotech units shipped with a piece of
| velcro to eliminate wobble. I think that Memotech kit had a
| great aesthetic.
|
| https://www.nightfallcrew.com/27/09/2013/memotech-
| memopack-1...
| [deleted]
| YZF wrote:
| ZX81 -> ZX Spectrum -> Atari 520ST
|
| It wasn't the first computer I used but it was the first
| computer I owned. I still have all the hardware somewhere
| (including minutia like the ZX Microdrive sitting on my desk
| right now), I have some books as well ;)
| TacticalCoder wrote:
| > I'm glad I still have it, and the Spectrum and Amiga's that
| followed.
|
| I wonder how many of us still have them all... I probably sound
| like a broken record at this time but I still have my Atari 600
| XL, Commodore 128 (which I was only using in C64 mode) and
| Commodore Amiga.
|
| The 600 XL and 128 are still working and the Amiga is probably
| easy to fix.
| cesaref wrote:
| I ditched almost all my old computers as I upgraded, but i've
| still got my ZX-81 with a dk'tronics graphics rom, that was a
| killer combination in 1982 or whenever!
|
| The ones that have left the building include C64, C128D,
| Amiga 1000, Amiga 500, before I got my first 'proper'
| computer, a Mac IIcx which I had for many years running
| Logic. I'd like to say those were the days, but actually i
| get much more done and have more fun with modern computers,
| it's really just nostalgia for simpler times...
| TacticalCoder wrote:
| Oh totally: I'm not using them and much prefer my modern
| setup and its 3840x1600 monitor ; )
|
| I just found these old machines of mine in a garage during
| the first Covid lockdown and decided to try them out and
| found out they were still working (still had an old CRT TV
| laying around).
| vram22 wrote:
| I agree about the nostalgia, and will also add (differing),
| that at least in some ways, those were more fun times ...
| because the overhead of all this modern complexity
| (although it sure does confer greater features and power),
| does kill off some of the fun.
| FabHK wrote:
| > Incredibly, the ZX81 hardware and software scene is still
| alive.
|
| Indeed. Here the German ZX81 User group:
|
| http://www.zx81.de/
|
| http://www.zx81.de/zxcms/English.html
|
| They've managed to turn a ZX81 into a web server:
|
| http://zx81-siggi.zx-team.org/ZxTeaM
|
| (I hope it survives being HN'd...)
| MaxBarraclough wrote:
| > (I hope it survives being HN'd...)
|
| Looks like we sunk it.
| nickt wrote:
| Again!
|
| https://news.ycombinator.com/item?id=25638936
| cr212 wrote:
| I think it was the ZX81 (and later the Spectrum) where my brother
| and I had it hooked up to the mains on my parent's boat. The
| problem was there was only one 12V battery (via a voltage
| regulator) which not only powered lights and our computer, but
| also served the engine. If we were sailing and the wind dropped,
| we established a protocol where my Dad would have to give
| sufficient notice for us to save whatever we were working on to
| tape before he started the engine, as the starter motor drew
| enough current to dip the voltage below the 9V the ZX81 needed,
| thus causing it to crash. And of course, RAM wobble wasn't helped
| if there were heavy waves. It's amazing what we put up with just
| to get some computing time.
| davidrupp wrote:
| I did my first programming on one of these, translating text
| games (bitmapped graphics were possible with the 16K RAM pack,
| but I didn't have one of those for a long time) from a book of
| them written for the TRS-80. The combination of having to
| translate between dialects of BASIC and having to "translate"
| game features to match the ZX81's reduced capabilities was a
| great practical exercise in inventiveness and perseverance. I
| particularly remember a Star Trek combat game that ended up
| taking up so much of the onboard RAM (one whole kilobyte!) that
| it started eating into the screen buffer, reducing the number of
| lines the computer could display. I think I ended up with one or
| two lines of text telling me what was going on, and one line of
| input for my next command.
|
| Today, I work at Amazon as a senior software engineer. I believe
| having access to this affordable[1] computer as a teenager helped
| make that career path possible.
|
| [1] The TRS-80 and other contemporaries of the ZX81 were very
| not-affordable to my family at the time.
| canada_dry wrote:
| Speaking of modified ZX81's... I re-wired a full sized keyboard
| (I think I was ~15 at the time) to replace the original [i]
|
| [i] https://i.imgur.com/MpoQP4u.jpg
|
| The ZX81 along with the Z80 microprocessor book from Radio Shack
| [ii] were the _gateway drugs_ that focused my career direction!
|
| [ii] https://www.cpc-
| power.com/cpcarchives/index.php?page=article...
|
| I'm retired now, but my career went from jr. programmer (in
| banking) thru to executive level IT management. A great ride
| thanks in large part to that inexpensive UK computer!
| nickcw wrote:
| I just posted a pic of my highly modified ZX81 here
|
| https://mobile.twitter.com/njcw/status/1368566103933337603
|
| In honour of the #zx81 40th bday I got mine out the attic. I
| modified it heavily to have external keyboard, programmable
| character generator and easy access to swap the ROM. I killed it
| trying to upgrade to 48k RAM but I haven't the heart to dispose
| of my first computing love!
|
| In those days I obviously had no fear cutting into the case and
| soldering stuff on the motherboard! I'm not that brave any more.
| nickt wrote:
| Looks very retro cyberdeck!
| JNRowe wrote:
| What is the keyboard in your photo? The lack of oversized keys
| has me confused.
|
| Also, love that it is a 3,284,741 byte image of a ZX81. And the
| ,/< because -- presumably -- a dog ate your 1 ;)
| nickcw wrote:
| It is a cast off relay keyboard - easy to wire up to the
| ZX81. I don't recall where it came from, but I don't think it
| ever had a 1 key as was common on typewriters back then (you
| just used l instead).
| JNRowe wrote:
| Oh, I had absolutely no idea about that. I naively assumed
| the current number row was original. You've sent me down a
| rabbit hole that so far includes using f and L to produce a
| PS too, thanks!
|
| For others like me the qwerty page1 has some info, and some
| examples of original layouts without a 1 key2.
|
| 1 https://en.m.wikipedia.org/wiki/Qwerty
|
| 2 https://en.m.wikipedia.org/wiki/File:QWERTY_1878.png
| virgulino wrote:
| The first computer I saw [0], and the first computer at home [1],
| were Brazilian clones of the Sinclair ZX81.
|
| That's where I learned to program, in Basic. It changed my life.
|
| Thanks Sinclair.
|
| 0 https://en.wikipedia.org/wiki/TK82C 1
| https://pt.wikipedia.org/wiki/CP200
|
| [ https://news.ycombinator.com/item?id=26360746 ]
| trynton wrote:
| According to something I read somewhere. The ZX81 floating
| routines did incorperate some unique math:
|
| (2^32) - ((2^32)-1) did not return 1
|
| And the group of Cambridge mathamaticians that wrote the ROM
| turned out to be one man.
|
| "ZX81 ROM Assembly Listing"
|
| https://www.tablix.org/~avian/spectrum/rom/zx81.htm
| rwmj wrote:
| I just tried it on the ZX81 online emulator:
| http://www.zx81stuff.org.uk/zx81/jtyone.html
|
| You have to type the following sequence of keys:
| P [Shift]I 2 [Shift]H 3 2 [Shift]O - [Shift]I
| [Shift]I 2 [Shift]H 3 2 [Shift]O - 1 [Shift]O
| Enter
|
| which should appear as: PRINT
| (2**32)-((2**32)-1)
|
| It prints 0 which is not the expected answer! (The 0/0 at the
| bottom of the screeen is an OK message, the answer is printed
| in the top left corner). I think this isn't necessarily a bug,
| it's because the computer used something similar to modern
| single precision floating point.
|
| Also try this (SQR is entered as: [Shift]Enter H):
| PRINT SQR 0.25
|
| On the emulator it looks like the bug has been fixed, but on
| early models of the real hardware it would give a completely
| bogus result.
|
| I think what was interesting was it used a kind of bytecode to
| run maths routines (similar to the Apple II's SWEET16 code).
| zokier wrote:
| 0 is actually what I'd expect as an answer. Even on very
| modern Python you get In [1]: 2.0**64 -
| (2.0**64-1.0) Out[1]: 0.0
|
| Thats how floats behave like with operands that differ
| greatly in magnitude. Also this In [2]:
| 2.0**64 == (2.0**64 - 1.0) Out[2]: True
| trynton wrote:
| > 0 is actually what I'd expect as an answer. Even on very
| modern Python you get
|
| Given a four byte mantissa, it should be 1 for anything
| under and equal to 2^32 and 0 for anything over 2^32.
| Instead it outputted some random number. A bug in checking
| the flags or some-such. Or maybe a bug in the float to
| string routine.
| zokier wrote:
| The sign takes one bit off the mantissa.
| anthk wrote:
| "1" in Scheme: >(- (expt 2 64) (- (expt 2
| 64) 1)) 1
|
| http://people.csail.mit.edu/jaffer/SCM.html
| trynton wrote:
| According to the link to ""ZX81 ROM Assembly Listing"", it
| used a "FORTH-like, stack-based language.". Amazing all the
| same how they managed to squeeze so much out of so little.
| klelatti wrote:
| One of the things that distinguished the ZX81 from its
| predecessor the ZX80 was the fact that the screen didn't go off
| when your program was running, which made it much more useful.
| The CPU was still driving the screen but interrupts ensured that
| it was doing so when needed so actual code execution was limited
| to times when it wasn't needed for the screen.
|
| This of course made it exceedingly slow. Not helped by the fact
| that the BASIC - squeezed into 8k - was also very slow.
|
| You could write a surprisingly big program in the 1k RAM though
| due to the fact that all the BASIC keywords were stored as one
| byte - and had to be entered using one keypress. Which given the
| quality of the key (not actually keys) board was a relief.
|
| Truly a machine built down to a price, but with considerable
| ingenuity!
| forinti wrote:
| You could, for 170 pounds, get an Acorn Atom. It had 2KB of RAM
| (twice as much!), a proper keyboard, an excellent BASIC, and a
| video chip.
| klelatti wrote:
| Wikipedia says that would be over PS700 in 2019 money - too
| much for a 15 year old!
|
| Besides the PS170 Atom only had Integer Basic - we had real
| (sort of) floating point.
|
| I'm still jealous of anyone who had an Atom though.
| [deleted]
| andromaton wrote:
| And the A in ARM stands for Acorn. And the ARM1 was based
| on a Berkeley design, now on version 5 (Risc V).
| Connections, connections everywhere.
| ourcat wrote:
| I had one of these at age 10. I still have it (at age 50) and it
| still works. Also the printer and a roll of paper.
|
| Whenever people ask me what my earliest memory is, I say the 16k
| RAM Pack. :)
| Theodores wrote:
| My inner nine year old envies you for having the printer and
| paper.
|
| I will memorise your earliest memory joke.
| Twirrim wrote:
| I'm 40, I vaguely remember my parents had one at some stage,
| and I'm reasonably sure it had the 16k RAM pack, but the first
| I really remember is the ZX Spectrum with the 48K ram, and
| rubber keys. First thing I ever programmed, though mostly I
| wanted to play Chucky Egg, Manic Miner, Granny's Garden etc.
| ourcat wrote:
| I never had a 'Speccy'.
|
| Some old friends of mine wrote a song ages ago about the
| effect those machines had on us all, called "Hey Hey 16k" -
| https://www.youtube.com/watch?v=Ts96J7HhO28
| elvis70 wrote:
| The 16k RAM Pack, a life lesson in itself.
| nickt wrote:
| I recently restored a ZX Printer, bit of a pain but mostly
| because the belts disintegrate on touch. You can buy new ones
| though [1] and you see them on eBay too sometimes.
|
| Worth the resto for the wonderful noise they make!
|
| [1] https://www.sellmyretro.com/offer/details/zx-printer-
| replace...
| zeckalpha wrote:
| I have a photo of my grandfather with a ZX81, though I never saw
| him use it. By the time I was around, he had an Apple //e and an
| IBM PS/2.
| tyingq wrote:
| I remember them being wildly popular at first, because they
| were so much cheaper than other 8 bit computers. Then, price
| wars made computers with more memory and a better keyboard more
| competitive, and you started seeing much less of the ZX81.
| dcminter wrote:
| If like me you have fond memories of the ZX81 (though not perhaps
| of the keyboard), then you might find this print interesting:
|
| http://www.alisoneldred.com/john-harris/fine-art-prints-1/sc...
| Theodores wrote:
| Good find. For me the artwork looks better as the manual with
| the red writing.
| dcminter wrote:
| I found it a while back and couldn't resist. I'm having it
| framed at the moment. I have the original manual from my own
| ZX81 (from which I taught myself to program) so I get the
| best of both worlds there.
|
| I plan to have the print visible in the background on the
| webcam for work meetings to earn a bit of nerd cred.
| Theodores wrote:
| It deserves to be licensed as a desktop wallpaper in Ubuntu
| or another operating system.
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