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Last modified 2026-02-01

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Sinclair ZX81

A picture of Sinclair ZX81

SPECIFICATIONS

GENERAL
Type:8-bit home computer
CPU:Zilog Z80 @ 3.5 MHz
Operating system(s):Sinclair Basic
Memory:ROM: 8 KB
RAM: 1 KB (Expandable to 64 KB)
Power supply:7.5-10 VDC (9 VDC nominal) from external PSU. Internal 5 V regulator
Current drain / power consumption:Max 600 mA
Dimensions (W*H*D):167*40*175 mm (6.57*1.57*6.89")
Weight:350 g (12.34)




I/O
Keyboard:Integrated membrane keyboard
Graphics: Text: 32*22 characters
Graphics: 64*44 pixels, black and white
Audio:No
Storage:Tape recorder (250 bd)
External I/O ports / connectors:
Tape I/O:   ?
RF out:   ?
Z80 bus:   ?-pin edge connector
Other:




MISCELLANEOUS
Manufactured:UK, 1981-1982 (Discontinued)
Additional info: Also sold in the US as Timex Sinclair 1000
New price 1982 in Sweden: SEK 895:- (Kit), SEK 995:- (Factory built)
New price, february 1984 in Sweden: SEK 795:- (Factory built)
Related documents:
Modifications and fixes:
Notable "ham" software: "Callsearch" - By G6ENX (Requires 16K RAM expansion)
"Logbook" - By G6ENX (Requires 16K RAM expansion)
"OSCAR-RS Orbits" - By G8YT (Requires 16K RAM expansion)
"QTH locator/Contest score" - By G4ANB and G3UBX
"Distance & bearing" - By G4ANB and G3UBX
"Sprog finder" - By G4ANB and G3UBX
Reviews:
Some options / Accessories:
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A picture of Sinclair ZX81 motherboard