4 ms·

How the ZX80 Works (2019)

38 points by mariuz 5mo ago

PaulHoule 5mo ago
This book https://archive.org/details/Cheap_Video_Cookbook_Don_Lancaster https://archive.org/details/Cheap_Video_Cookbook_Don_Lancast... talks about how to build homebrew video systems similar to the ZX80.
- pjmlp 5mo ago
  They were everywhere back then, on electronic stores, the maker movement of modern days feels like a revival back to those days.
gxd 5mo ago
Despite quickly becoming obsolete, the early ZX computers (ZX80 and ZX81) were a marvel of cost-benefit at the time. Most people had no access to computing of any kind... The difference between no computing and a machine that can perform thousands of operations per second is massive.
- pjmlp 5mo ago
  When I finally got one, it was already the Timex 2068 (48K clone with some extras), but it got certainly plenty of use, not only games.
ofrzeta 5mo ago
Yeah, let's go back to the ZX80 (or 81) because we can all afford 1kb RAM (some of use might even get the 16kb extension).
- jeffreygoesto 5mo ago
  You mean. I should offer my Memopak 16kB with original box on eBay and see how it goes? A small yacht maybe?
  - mrlonglong 4mo ago
    if you can stop it falling off the back ...
    - lproven 4mo ago
      Blu-Tak FTW.
RetroTechie 5mo ago
(2019, who cares :-) Excellent & detailed write-up. The later ZX81 is best regarded as a ZX80 with some minor (but important!) tweaks. Hard to understand, is effect of the semi-separated data buses (D0..D7 vs D0'..D7'). This is an intricate play between cpu, ROM code, signal timing & external hardware (external to cpu, that is). Aeons ago I designed a ZX81 ULA replacement in programmable logic, and couldn't shake the feeling that with adjusted signal timing, it might be possible to get things working on a single 'unified' data bus. If I ever touch this again, I'd have a serious look at that. But I suspect the way it was done, is because the signal timings allow for very slow ROMs and/or RAMs (up to ~450 ns iirc). This was important, since (to keep costs down) Sir Clive was buying memory ICs wherever he could find 'em cheap. Remember £99 for a real, user-programmable computer was the ZX80's #1 selling point. As gxd noted, this was when people did not have computers in their homes. No PC, laptop, tablet or smartphone. NONE. Perhaps a pong console if lucky. So people were very curious & eager to find out what could be done with such a machine. Regardless its limitations, or how crappy its keyboard ;-)
anonymousiam 5mo ago
Over 40 years ago I worked with a guy who had bought a ZX80, and had designed and built his own expansion systems for it. Eventually it reached the point where it consumed most of the space in one of the rooms of his house. He kept the thing running for many years beyond the point where the technology was obsolete.
deleted 5mo ago
[deleted]
pjmlp 5mo ago
Back in the early 1980's this could also be bought at electronic shops and be mounted at home, DYI style. I remember seeing them on the electronics store my father used to go to, for work related components.

38 points by mariuz 5mo ago

This book https://archive.org/details/Cheap_Video_Cookbook_Don_Lancaster https://archive.org/details/Cheap_Video_Cookbook_Don_Lancast... talks about how to build homebrew video systems similar to the ZX80.

pjmlp 5mo ago
They were everywhere back then, on electronic stores, the maker movement of modern days feels like a revival back to those days.

gxd 5mo ago

Despite quickly becoming obsolete, the early ZX computers (ZX80 and ZX81) were a marvel of cost-benefit at the time. Most people had no access to computing of any kind... The difference between no computing and a machine that can perform thousands of operations per second is massive.

pjmlp 5mo ago
When I finally got one, it was already the Timex 2068 (48K clone with some extras), but it got certainly plenty of use, not only games.

ofrzeta 5mo ago

Yeah, let's go back to the ZX80 (or 81) because we can all afford 1kb RAM (some of use might even get the 16kb extension).

jeffreygoesto 5mo ago
You mean. I should offer my Memopak 16kB with original box on eBay and see how it goes? A small yacht maybe?
- mrlonglong 4mo ago
  if you can stop it falling off the back ...
  - lproven 4mo ago
    Blu-Tak FTW.

RetroTechie 5mo ago

(2019, who cares :-) Excellent & detailed write-up. The later ZX81 is best regarded as a ZX80 with some minor (but important!) tweaks. Hard to understand, is effect of the semi-separated data buses (D0..D7 vs D0'..D7'). This is an intricate play between cpu, ROM code, signal timing & external hardware (external to cpu, that is). Aeons ago I designed a ZX81 ULA replacement in programmable logic, and couldn't shake the feeling that with adjusted signal timing, it might be possible to get things working on a single 'unified' data bus. If I ever touch this again, I'd have a serious look at that. But I suspect the way it was done, is because the signal timings allow for very slow ROMs and/or RAMs (up to ~450 ns iirc). This was important, since (to keep costs down) Sir Clive was buying memory ICs wherever he could find 'em cheap. Remember £99 for a real, user-programmable computer was the ZX80's #1 selling point. As gxd noted, this was when people did not have computers in their homes. No PC, laptop, tablet or smartphone. NONE. Perhaps a pong console if lucky. So people were very curious & eager to find out what could be done with such a machine. Regardless its limitations, or how crappy its keyboard ;-)

anonymousiam 5mo ago

Over 40 years ago I worked with a guy who had bought a ZX80, and had designed and built his own expansion systems for it. Eventually it reached the point where it consumed most of the space in one of the rooms of his house. He kept the thing running for many years beyond the point where the technology was obsolete.

deleted 5mo ago

[deleted]

pjmlp 5mo ago

Back in the early 1980's this could also be bought at electronic shops and be mounted at home, DYI style. I remember seeing them on the electronics store my father used to go to, for work related components.