Released on 5 March 1981, the ZX81 was the successor to 1980s ZX80 and, like its predecessor, was based around a Z80 CPU. Two years later, in summer 1983, I bought my Oric1, my first home computer based around a 8-bit 6502A running at amazing CPU clock of 1 MHz. For a reference, next to the Oric1 logo, is Raspberry Pi Zero based around a 32-bit ARM11 running at CPU clock of 1 GHz. What an astonishing CPU clock rate gain over less than 4decades = 1000 time faster:
Fig.1: The Oric1 and, next to its logo, Raspberry Pi Zero
Fig.2: The Oric1 connectivity (Left to right): display output to drive a PAL UHF TV; RGB output on a 5 pin DIN 41524 socket; cassette recorder connector via a 7 Pin DIN 45329 socket; printer port, compatible with the then-standard Centronics parallel interface; expansion port allowing full access to the CPU's data address and control lines including external ROM and RAM access/expansion.
REF:- ZX81: https://en.wikipedia.org/wiki/ZX81
- Oric1: https://en.wikipedia.org/wiki/Oric
- MOS Technology 6502: https://en.wikipedia.org/wiki/MOS_Technology_6502
- Centronics: https://en.wikipedia.org/wiki/Centronics
- Raspberry Pi Zero: https://en.wikipedia.org/wiki/Raspberry_Pi#Pi_Zero
