The Sinclair ZX81 was released 40 years ago today #VintageComputing
The Sinclair ZX81, the first mass marketed computer in the UK, was launched 40 years ago today. Compared to its successors, it was very modest in specifications (via Wikipedia):
The ZX81 has a base configuration of 1 KB of on-board memory that can officially be expanded externally to 16 KB. Its single circuit board is housed inside a wedge-shaped plastic case. There are only three other onboard chips: a 3.5 MHz Z80A 8-bit microprocessor from NEC, an uncommitted logic array (ULA) chip from Ferranti, and an 8 KB ROM providing a simple BASIC interpreter. The entire machine weighs just 350 grams (12 oz).
The ULA chip provides many key functions:
Synchronising the screen display;
Generating a 6.5 MHz clock, from which a 3.25 MHz clock is derived for the processor;
Outputting an audio signal to a cassette recorder in SAVE mode;
Processing the incoming cassette audio signal in LOAD mode;
Sensing keystrokes;
Using memory addresses provided by the CPU to decide when ROM and RAM should be active;
Controlling general system timing.
Both the ZX81 and its predecessor, the ZX80, have a significant drawback in the way that they handle visual output. Neither machine has enough processing power to run at full speed and simultaneously maintain the screen display. On the ZX80, this means that the screen goes blank every time the machine carries out a computation and causes an irritating flicker whenever a shorter computation – such as processing a keystroke – takes place.
Happy Birthday!
Adafruit publishes a wide range of writing and video content, including interviews and reporting on the maker market and the wider technology world. Our standards page is intended as a guide to best practices that Adafruit uses, as well as an outline of the ethical standards Adafruit aspires to. While Adafruit is not an independent journalistic institution, Adafruit strives to be a fair, informative, and positive voice within the community – check it out here: adafruit.com/editorialstandards
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.
Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7pm ET! To join, head over to YouTube and check out the show’s live chat – we’ll post the link there.
Python for Microcontrollers — Python on Microcontrollers Newsletter: MicroPython Pico W Bluetooth, CircuitPython 8.0.4 and much more! #CircuitPython #Python #micropython @ThePSF @Raspberry_Pi
