Raspberry Pi brings back memories of the ZX81

The recent Pi Day educational opportunities for workshops to develop STEM interest in young learners brought to mind many memories of my own childhood and early computer access that led me to study computer science and engineering when I finally got to college.


My earliest experiences with computers were during my fathers doctoral studies, were we would take large boxes of pre-punched cards to the data center, where these cards would be taken by computer scientists into special rooms kept clean and chilled to protect massive computing systems – almost like some type of priest taking an offering to the alter of some technology god. The cards contained programs and data and were fed sequentially through optical readers that input the information and then printed out the results onto tractor-fed paper (assuming things went right). The issue of “hanging shads” was not new during the Florida election result tabulation at all, because card punching was not always successful and a single partially-punched card around card #4000 would snag and abort the entire run – resulting in a large unsorted box of cards being delivered back to us to re-punch the mangled card, restack the entire batch, and return to schedule a second try…or third…or twentieth…

Students and even their teachers today find the idea of a computer with such difficult interactions to be almost comical, when I start illustrating the use of single-chip computers with far greater computing potential costing less than $50 for the entire computer compared to old multi-million-dollar systems attended to in their chilled sanctums far away from children##Q##s hands. For me, those massive systems were glimpsed through doorways as the technicians carried our latest cards into their digital masters while we waited to see if our offering to the data gods was accepted as worthy enough to process or rejected at card #5412 for another try. However, in 1981, the Timex Sinclair ZX81 kit computer came out in the UK and my parents ordered one and a new 30watt soldering iron for me to build my own computer!

ZX-81 Kit

By modern standards, this was a woefully basic computer not worthy of performing the functions of a digital watch, but once it arrived I began to assemble the components, solder together the pieces onto the board, and eventually arrived at a computer I could connect to a tape recorder (program and data storage) and a television (display) and run a program of my own creation! As “HELLO WORLD” echoed in the glowing phosphor I knew it was possible to build far more and so began a life-long journey I am now passing along through the STEMulate Learning workshops!

Raspberry Pi Workshop computers

Today, I regularly use single-chip computers like the Raspberry Pi, which also came from the UK, to teach the next generation about the potential for their own creations – adding wires and other components to allow them to write web-accessible controls for sensors and multi-colored LED illuminators. Comparing the Raspberry Pi to the ZX81 shows many similarities although the 30 year difference illustrates improvements as well:

ZX81 Rasberry Pi
CPU Zilog Z80 3.25MHz ARM 700MHz
Video Monochrome TV RF Modulator HDMI and Composite
Graphics 64×48 pixels monochrome 1080p HD
RAM 1kB 512MB
Keyboard Built-in membrane USB keyboard and mouse
Storage Audio cassette SD Card or USB HDD
Network n/a 100GB Ethernet, or USB WiFi/Bluetooth
O/S Proprietary embedded Linux (Raspbian) and others
Language Sinclair ANSI BASIC Python, but others work under Linux
Cost £ 49.95 £ 25 ($35 USD)

The Raspberry Pi also allows direct connection to external electronics through its GPIO interface, making it an exceptional platform for instruction in electronics, robotics, and many other areas beyond computer science and programming.

Timex Sinclair ZX81 Computer Raspberry Pi

In its accessibility to children, todays Raspberry Pi reminds me of the ZX81 from my own childhood – imagine what our children will see 30 yeas from now!

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