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Sinclair ZX81 Computer

Manufacturer Sinclair Research
Model ZX81
Date Announced 1981
Date Canceled Unknown
Number Produced 1 million +
Country of Origin UK
Price $200
Current Value $0 to $50
Processor Zilog Z80
Speed 3 MHz
RAM 1K expandable to 56K
Storage External Cassette Tape
Expansion RAM Packs and not much else
Bus Single expansion port
Video Up to 256x192 graphics with additional memory
I/O Various through the expansion port including Parallel and Serial
OS Options N/A
Notes The Sinclair ZX-81 (also sold by Timex as the Timex Sinclair 1000) was a very compact Z80 based machine with a membrane keyboard. It was designed and built to be inexpensive and, as such, it was a very common first computer for many people. THe ZX81 was an upgrade to the ZX80 which had half the ROM.
Related Items in Collection A few docs and a few cables
Related Items Wanted Tape player, tape software, etc.

The Sinclair ZX81 came from the genius of Clive Sinclair and his desire to bring computing to the masses. The ZX81 was a simple, rugged and very inexpensive computer sold both as an easy-to-build kit and as a fully assembled system.

This machine was not intended to serve any business functions. It was a home machine from the outset designed with the goal of making computing accessible.

Sinclair ZX81 in box

The Sinclair ZX81 in my collection is boxed in it's original shipping carton.

Sinclair ZX81 docs

Pictured are the documents that this unit came with. In addition to those I have a metric ton of books and other documentation donated by Trenton Henry.

(Submitted February 11, 2012 09:19:14 by Juan)

I was the Librarian for the North America Timex-Sinclair Association between 1982-1983, I own 20 ZX81s, several thermal printers and others that print on plain paper, a speech module, High Resolution pack, 16 , 32 and 64 Memotech RAM packs, external keyboards, ROM burning module, Assembly and other ROMs, Quick Save filter modules to save data 20 times faster, one of my ZX81s is the very first version ever issued, it says inside, in many I replaced the small heat sink by a much bigger one for more reliable working, printer interface so I could use a Canon BJ-200 printer, I also have the OPUS module for saving onto diskettes, etc, etc., I even wrote an article (for which I was paid 100 bucks) for a 1983 issue of SYNC magazine on using it for archaeological research, I continued using it till 1998 when internet forced me to switch to PCs. Sir Clive Sinclair was a genius...

(Submitted December 19, 2011 14:57:15 by Marat)

I got sinclair zx81 ! NEW!! on the box newer open!

I wona sell ! Im from spain!

(Submitted March 5, 2011 18:53:54 by Mary)

I am selling a nearly new Timex Sinclair ZX81 personal computer with all equipment, operating supplement manual, programming book, perfect condition reference card, and a book separately purchased called IDEA BOOK specifically written for this computer. It includes 50 ready-to-run educational programs, written by David H. Ahl, 1983. Any interest or know of anyone who may be? Thank you.

(Submitted February 22, 2011 10:54:52 by ct4er)

I have had two ZX81 with the 16MB memory and later with32MB. The last one is still working.

(Submitted February 22, 2011 14:28:04 by Dave D)

I bought mine as a kit to save $20 I think. The diagram printed on the circuit board was wrong and it cost me $10 to send it back to them to get it repaired. I have the 16k expansion, a whole lot of Sync Magazines that I typed the programs into it from and a tape recorder control switch that I built in order to start the tape up after the tone it used as a signal. I bought the kit for $99 and later bought the 16k pak and several program tapes when a store was closing for around $10. The pak at the time was selling for $99. What fun times.

(Submitted December 15, 2010 08:01:07 by RapidAssistant)

Inherited my ZX81 from another family member. The programming manual was complete gobbledegook to an 8-year old at the time - which assumed you knew about maths at a level I didn't learn about until high school! Remember you had to memorise the volume setting of the tape player for every game, and the long minutes of anticipation staring at the stripey pattern trembling on the TV screen to see if you had been successful or least they now come up instantly on the Android emulator on my mobile phone!

(Submitted June 4, 2010 17:47:55 by Russell Hedges)

I had, or perhaps have, a Micro-Ace. It was made in the U.S. I thought that it was a licensed copy of the Sinclair, later I heard that it was a pirate copy. It took the 16K memory expansion that I eventually found at a thrift shop. I used it in my car, it ran fine from the 12 Volts! Back when prtable computing seemed pretty cool.

(Submitted April 29, 2010 02:42:31 by ZX81Museum)

The ZX81 Museum was set-up to preserve and showcase original Sinclair branded ZX81 hardware, software and literature. The museum has since expanded to include ZX81 software from other publishers of the time and a variety of ZX81 programming and reference books. The collection dates from 1981 to 1983 and features the complete Sinclair-branded software series.

(Submitted April 26, 2010 14:09:25 by Gerry Williams)

can anyone advise if you can connect a zx81 to a modern monitor that has a vga input

(Submitted November 11, 2009 05:59:46 by T)

Had more fun with this machine than I ever did with ANY after that. Great days.

(Submitted August 27, 2009 20:20:27 by Ben)

the zx80 and 81 were great systems in the early 80's I bought both as they came out from a computer shop in Cambridge, England while stationed at RAF Lakenheath. I turned the ZX81 mobile by hooking directly into an old CRT I yanked out of a portable radio/TV combo supplied power by tying 6 volt latern batteriesWe spent hours keying in code for games from books I bought.had the printer 32k memory module, soldered the full size keyboard directly to the motherboard, even installed a character ROM that was available that gave you the pacman,asteroids,space-invaders, and other games of those days. I would not be in the career I am in today if it were not for getting my start on this little gem from my past!

(Submitted January 31, 2009 11:35:38 by DRaken)

Ah yes, the ZX81, bought from several months' allowance. Having found out that 1K isn't very much, and having not-so-much money left, I bought a cheap 16K expansion of disputable origin. It turned out to suffer from what we called wobbling, i.e. shortly losing contact and therefore content when the computer was moved a fraction of an inch. I remember trying to enter some longer program listings like that, avoiding saving intermediate versions because the tape recorder was s-l-o-w. Those were the days we were still computer monks.

(Submitted January 21, 2009 09:45:09 by Geoff Rowney)

I notice that one of your contributers says, You can now connect SD cards and Hard Drives to the ZX81. In view of the unreliability of using a tape recorder to load programs, please can anyone tell me how I can obtain or build hardware to enable use of a memory card or USB Stick?

(Submitted December 6, 2008 18:31:35 by R. Olivarez)

Back in the mid 1980s, while I was in the land of Oz, I remember seeing a book on artificial intelligence programs for the Sinclair and Timex computers.

Does anyone have a copy of it or where I can get a copy of it? Seems it is out of print, and ot available in the U.S.

Please contact me at:, if you have a copy of it or know anything about the book and how I can get a copy of it.

Thanks, R.

(Submitted November 15, 2008 05:34:38 by Eddie Zayas)

I have for sale a Sinclair QL, plus a lot of software including a Flight Simulator, games,, microdrives, etc. for sale. Just contact me: or call me at 939-579-5730. I owned all the Sinclair's computers including the ZX81, TS1000, TS1500, TS2048, Spectrum and the last one, Sinclair QL.

(Submitted October 12, 2008 14:31:15 by Nick Yates)

Briliant little computer, this was what started me off in computer the only draw back with this computer was that its heat sink melted burnt a hole in my trousers and I still have the burn to prove it!, The ZX81, I still currently have 3 one with a 16K ram pack and was the first computer I started programming with... The only other issue I did not like with the ZX81/80 and spectrums is the way you generate the program with select certain keypresses for commands..

(Submitted September 17, 2008 11:54:31 by lodger)

I discovered the ZX81 back in the mid-80s, when C64s were all the rage (I also had one). But one of our neighbours had this ZX81 and borrowed it to me. It had only 1K RAM, but there were books in the local library that had BASIC listings of 1K apps and games. I never really owned one until a few weeks ago, but this machine is no. 3 on my personal favourite list (C64 is 1st, then the Amiga 1200, then the ZX81). What makes this computer so appealing is the small size, the futuristic design and the (still living) community of ZX81 enthusiasts. Thank god I found a 32K Rampack on ebay ... ;)

(Submitted January 30, 2008 17:17:42 by ANDRE)

I would like to correct some errors. SPEED: 3.5 Mhz RAM: 1KB on ZX81, 2KB on TS1000, up to 64KB EXPANSION: Rampack, printer, colorpack, sound, RS232 etc... VIDEO: 32 X 24 (22), 64 X 44, 256 X 192 (software) New software is released every month on the web. There are ZX81 emulators available even for the Nintendo DS and the Sony PSP. Goodby(t)e, ANDRE***

(Submitted September 20, 2007 08:19:10 by JOE JAMES)


(Submitted August 22, 2007 19:43:07 by James G. DuPuy)

I have a ZX-81 that I built, and a TS-1000. I figured a way to connect the video directly into the video amp of a tv for a rock solid picture. I have a 2068 with all the goodies. I used to write a lot of software for them. I also have a QL. The ZX Printer did use the aluminum coated paper but it did not burn the paper, it simply vaporized the aluminum coating to expose the dark paper underneith. The rolls were a bit pricy. The 2040 Timex Printer was thermal and could use the same paper as a printer made by Tandy for their little color computer's printer. I used to repair all this stuff too years back. We had a nice computer group in Cleveland OH. Several of us still meet most months but rarely discuss the TS or Sinclair anymore. All mine still work, however!

(Submitted August 12, 2007 19:42:07 by (a href=mailto:zxspectrum128atgmaildotcom)Bruno Florindo(/a))

I'm a Sinclair collector and I have all the Sinclair machines that were sold, plus all the Timex Sinclair computers. I'm still collecting books, magazines and peripherals. The website has a very active community of TS1000 users. As of today, they're still developing new hardware projects. You can now connect SD cards and Hard Drives to the ZX81/TS1000. One TS1000 is now online as a webserver (using 16K of memory).'s ftp has scans of the Sync magazine, a must for all Timex Sinclair users. There are thousands of people out there who still use these computers today. Unfortunately the Sinclair scene was never strong in the U.S. Lots of people in the U.S. remember the C64, but not the Timex Sinclair. But in Europe that's another story.

(Submitted July 1, 2007 13:30:38 by Luiz Fernando)

I have a Brazilian version of the ZX-81, a CP- 200, made by Prologica, a Brazilian computer industry. I bought it in 1981, and it was my very first computer. I think it still works, but I havenŽt tested it in years. If youŽre interested in the appearance of such a computer, tell me and IŽll send you some photos! Regards!

(Submitted May 10, 2007 10:02:54 by Kelly)

Ihave the demo add on they used in stores. Is it worth anything.

(Submitted April 24, 2007 07:35:40 by BillK)

I can remember the TV output of the ZX-80/81 appearing on every TV set in an apartment complex (single, central antenna for all apartments. When the student living upstairs did homework the entire complex could watch the painful progress of text instead of the evening news or Ozzie and Harriet! For more readable output, my Osborne 1a (I think) came with a cable to connect to a TV. I never checked for interference with other TVs.

(Submitted January 6, 2007 13:17:46 by Simon Caygill)

From my earlier posting I was wrong the expansion packs did come from Memotech, not Memorex. I also have the DkTronics Keyboard.

(Submitted December 11, 2006 22:15:31 by David O)


In the UK, you're right the printer is what you described: The printer was not Thermal as stated. It was operated by Spark Erosion a high voltage spark was scanned across aluminum coated paper burning a black mark on a silver background.

HOWEVER, in the US the printer was a thermal printer. I should know.. I owned one.. :-)

(Submitted November 11, 2006 08:36:25 by maurice)

The printer was not Thermal as stated. It was operated by Spark Erosion a high voltage spark was scanned accross aluminium coated paper burning a black mark on a silver background.

(Submitted August 12, 2006 14:34:16 by Jeff)

I still have my ZX81, though I don't know if it still works...haven't tested in in years. The pre-built unit came with 1K of RAM and the kit came with 2K. I bought the kit and Sinclair shipped it with the WRONG instructions. I had to fight with them to get a replacement. They sent the assembled unit as the repalcement. I was bummed about that because the assembled unit used proprietary RAM chips and the kit used off the shelf stuff that was wired in parallel. You could get 16K of RAM for the kit machine at any electronics store and just wire the chips in parallel. I was 16 when I got my ZX81.

(Submitted August 5, 2006 05:30:05 by (a href=mailto:any)WB(/a))

I don't think Memorex made a ram-pack, wasn't it Memotech? Also, Zebra systems made a serial port and modem for it, which I bought and used to bbs for a couple years. A friend also had something like a 'stringy-floppy' which was a high speed tape drive I think.

(Submitted August 1, 2006 07:35:27 by Simon Caygill)

You will also find that Memorex released a 64K RAM pack and a Hi-Res Graphics pack. Did the MicroDrive work with the '81 or was this only for the Spectrum and QL (both missing from your list)??

(Submitted July 25, 2006 06:33:34 by Silvestre Oliveira)

Hi, please put a picture of Sinc. Get a one in zx8116k.jpg

Tks in advance, Sil

(Submitted July 10, 2006 10:36:04 by (a href=mailto:)sire(/a))

Not every ZX81 was sold as kit, they were also available preassembled. Mine is one of them.

(Submitted May 25, 2006 14:03:02 by downhill_without_brakes)

don't forget - the zx81 was orginally sold as a kit!

(Submitted April 1, 2006 05:34:03 by Andrew Hodson)

tape software

(Submitted October 11, 2005 11:16:16 by SkyZip)

I still own a ZX81, and besides the 16K rampack I also have the original zx81 thermo-printer. I kinda missed that on your page.

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