Sinclair Spectrum ZX81 ZX 81, 16K RAM expansion expansion, retro computer vintage collection, Clive Sinclair, CPU: NEC μPD780C at 3.25 MHz, compatible with Zilog Z80A, ROM: 8 kB, RAM: 1 kB, expandable up to 64 kB, Video: monochrome, text 32 columns × 24 lines, graphics 64 x 48 pixels, Keyboard: QWERTY 40 keys, membrane, Software included in ROM:  Sinclair BASIC, Expansion ports: 1 Expansion port, 1 Antenna (RF connection to TV), 2 Cassette recorder jacks (out and in)

Sinclair ZX81

The Sinclair ZX81 was a low-cost home computer manufactured in the United Kingdom by Sinclair Research. Introduced in 1981 as a successor to the Sinclair ZX80, the Sinclair ZX81 was produced until 1984. The computer was sold by mail order, as a mounting kit, but it could also be purchased already assembled.

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Sinclair ZX81 ZX 81, 16K RAM expansion expansion, vintage retro computer collectionSinclair Spectrum ZX81 ZX 81, 16K RAM expansion expansion, retro computer vintage collection, Clive Sinclair, CPU: NEC μPD780C at 3.25 MHz, compatible with Zilog Z80A, ROM: 8 kB, RAM: 1 kB, expandable up to 64 kB, Video: monochrome, text 32 columns × 24 lines, graphics 64 x 48 pixels,  Keyboard: QWERTY 40 keys, membrane, Software included in ROM: Sinclair BASIC, Expansion ports: 1 Expansion port, 1 Antenna (RF connection to TV), 2 Cassette recorder jack (out and in)

Missing from my vintage computer collection… were some Sinclair computers. So, I decided to purchase this retro computer, together with the 16 kB RAM expansion, as well as together with other computers in summer 2021. Here is the video of the purchased lot:

Start screen of the Sinclair ZX81

The start screen of the Sinclair ZX 81 is very simple and features a fixed cursor with the letter K. The image is available at the RF output (analog channel 36).

Sinclair ZX81, ZX 81, home screen, boot screen, boot screen, K cursor

Technical characteristics of the Sinclair ZX81

CPU: NEC μPD780C at 3.25 MHz, compatible with Zilog Z80A

ROM: 8 kB

RAM: 1 kB, expandable up to 64 kB

Video: monochrome, text 32 columns × 24 lines, graphics 64 x 48 pixels

Keyboard: QWERTY 40 keys, membrane

Software included in ROM: Sinclair BASIC

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Sinclair ZX81, rear port, expansion port, 16KB RAM, ZX 16K RAM

Expansion ports:

  • 1 Expansion port
  • 1 Antenna (RF connection to TV)
  • 2 Cassette recorder ports (out and in)
Sinclair ZX81, side ports, connectors, TV, EAR, MIC, 9VDC power supply

Dimensions: 16.7 cm (width) x 17.5 cm (depth) x 4 cm (height), 350 g

Sinclair ZX81 ZX 81, 16K RAM expansion expansion, retro computer vintage collection, Clive Sinclair, CPU: NEC μPD780C at 3.25 MHz, compatible with Zilog Z80A, ROM: 8 kB, RAM: 1 kB, expandable up to 64 kB, Video: monochrome, text 32 columns × 24 lines, graphics 64 x 48 pixels, Keyboard: QWERTY 40 keys, membrane, Software included in ROM:  Sinclair BASIC, Expansion ports: 1 Expansion port, 1 Antenna (RF connection to TV), 2 Cassette recorder jacks (out and in)

Emulation

It is possible to emulate the Sinclair ZX-81, on a common Windows PC, through the EightyOne emulator, which also emulates other Sinclair models. In this way, you can try to start programs and games, as well as program the back computer, in a simple and convenient way... without even owning the Sinclair ZX 81!

Power supply

The power supply of the Sinclair ZX81 is external. It generates a single 9 V voltage in direct current, unstabilized, with wide tolerance. The available current is 1.2 A. The connector is a 3.5 mm jack.

Sinclair ZX81, ZX 81, 9V power supply, transformer, RAM expansion Technical characteristics of the Sinclair ZX81 CPU: NEC μPD780C at 3.25 MHz, compatible with Zilog Z80A ROM: 8 kB RAM: 1 kB, expandable up to 64 kB Video: monochrome, text 32 columns × 24 lines, graphics 64 x 48 pixels Keyboard: QWERTY 40 keys, membrane Software included in ROM:  Sinclair BASIC Expansion ports: 1 Expansion port 1 Antenna (RF to TV connection) 2 Cassette recorder ports (out and in) Size: 16.7 cm (width) x 17.5 cm (depth) x 4 cm (height), 350 g

Papers

1. Sinclair ZX81 BASIC programming manual

2. Sinclair ZX-81 service and assembly manual

Date of entry into the collection: 08/25/2021

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