The ZX81 Turns 40 • Hacker News Board

Re: The ZX81 Turns 40

#11

Post by nickt » Sun, Mar 07, 2021, 2:59 PM UTC

In terms of ROI, the best £69.95 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...

Re: The ZX81 Turns 40

#12

Post by nickt » Sun, Mar 07, 2021, 3:02 PM UTC

nickcw wrote: post #8

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 n…

Looks very retro cyberdeck!

Re: The ZX81 Turns 40

#13

Post by nickt » Sun, Mar 07, 2021, 3:03 PM UTC

sys_64738 wrote: post #9

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.

> Commodore had the largest warehouse of these in North America by 1984

That sounds like a story, have any more details?

Re: The ZX81 Turns 40

#14

Post by TMWNN » Sun, Mar 07, 2021, 3:10 PM UTC

nickt wrote: post #13

sys_64738 wrote: post #9

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.

> Commodore had the largest warehouse of these in North America by 1984 That sounds like a story, have any more details?

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.

Re: The ZX81 Turns 40

#15

Post by criddell » Sun, Mar 07, 2021, 3:19 PM UTC

nickt wrote: post #11

In terms of ROI, the best £69.95 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, includi…

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.

Re: The ZX81 Turns 40

#16

Post by amelius » Sun, Mar 07, 2021, 3:22 PM UTC

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 :(

Re: The ZX81 Turns 40

#17

Post by analog31 » Sun, Mar 07, 2021, 3:27 PM UTC

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.

Re: The ZX81 Turns 40

#18

Post by FabHK » Sun, Mar 07, 2021, 3:32 PM UTC

nickt wrote: post #11

In terms of ROI, the best £69.95 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, includi…

> 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…)

Re: The ZX81 Turns 40

#19

Post by trynton » Sun, Mar 07, 2021, 3:32 PM UTC

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

Re: The ZX81 Turns 40

#20

Post by klelatti » Sun, Mar 07, 2021, 3:34 PM UTC

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!